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OpenGL Confused: Very large environments

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I've got an idea for a 3D application, but I'm trying to understand how I'm going to get this to work. The 3D scene created with OpenGL uses 32bit integers. What if the environment that I want to render is bigger than this? I need to use 64bit integers to render a 3D model a certain distance away from the "camera". I've played games like Frontier First Encounters that render huge environments in 3D and I'm trying to understand how this is done without having to jump through many hoops... anyone tried anything like this before?

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I've never actually done it myself, but the principle is pretty simple, If some thing is close, you should render a high poly version of the model, and if some thing is far away, you should only render a low poly version of the model. THis is called Level of Detail (LOD).

Afaik openGL uses float for distance.. So I really don't see how thats a problem. If it's because of your own map format, you should consider to split your map into regions.

Hope this helps :)

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If you want to render a truly huge scene, such as a realistic-scale solar system, or worse yet, universe, then you have to use some sort of coordinate hierarchy.

The idea is that you might model the Earth in metres, and attach it to the solar system, which is modeled in kilometres. The solar system in turn is attached to the milky way, which is modeled in light-years, which is connected to the local cluster, measured in millions of lightyears.

When you go to render the scene, you traverse the hierarchy downwards, and at each level, a 32-bit float has plenty of precision.

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Original post by Anessen
The 3D scene created with OpenGL uses 32bit integers. What if the environment that I want to render is bigger than this? I need to use 64bit integers to render a 3D model a certain distance away from the "camera".


Where does it use integers?

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I've had a similar problem with a game I'm working on right now. You, probably, won't need to go as far as I have to solve the problem. Work out how large your game world (that is, one area of it at a time) and decide your units from there. In case you have ran into an actual problem with why floats are bad (you will want to be using floats, not integers in OpenGL, unless maybe you're on an embedded platform using OpenGL ES), this is my solution:

In my game I've divided the world up into zones - each zone is it's own coordinate system, but it has a 3D integer vector for it's location rather than a 32bit float or matrix transform - that way I get perfect precision for a zone's location. Each zone is 1000x1000x1000 units (-500 to 500), and that's float. Done it like this so I have perfect precision at all times, whilst not having too many zones (solar system...big place). It's all stored in a hash map for quick lookup and so I don't need to have zones exist that don't actually have anything in them. Dynamically create/destroy them as objects pass in and out of them. Rendering far away zones is done with some manual placement and scaling on the model view per zone - precision doesn't matter for rendering far off objects really, not in my case. For very far away zones I can just render them as a star, or not at all. For the record it's an outer space game. I worked out that just travelling earth-moon distance would put me well outside of decent precision, and I'm working in 1 unit is 1km! Sounds overkill, but it works nicely having 1Mmx1Mmx1Mm zones - as I only need good precision down to around 1m.

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Thanks for your responses!

And yeah I meant float for actually rendering the scene, the world coordinates of the objects are stored as integers. I will need to use LODs for objects otherwise the poly count is going to go just insane for a start.

What I am making a game that would have to model a whole solar system at a time in real scale. What I am having problems understanding is how you can get enough precision to render this scene using float values, because the player's movement must be smooth relative to close objects but at the same time I can see the 3D models of objects that are many thousands of kilometers away (very large planets, stars etc).

I understand that I can model the locations of objects in a very large environment using a coordinate hierarchy, basically subdividing out grid spaces. What I'm having problems with is drawing that. I am quite new to 3D graphics (moving from 2D) so maybe I'm just missing something obvious here.

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You need to keep track of your objects with 64-bit floating point vectors and matrices to model an entire solar system, yet be able to move the camera to any position and see small details on each planet. I did this in my engine for exactly this reason.

You need to perform one other "trick" to make this work with current GPUs (because they only support 32-bit floating-point numbers). When your camera is near a particular planet, you need to make that object (or the camera) the "zero point", and subtract that position from the position of every object to compute "current pseudo-world coordinates positions". In most cases, it is easier to make the camera position the origin of this coordinate system, though that is a bit problematic if your engine supports multiple cameras (like mine does). Once you convert the positions of other objects into this new coordinate system, you can convert those positions to 32-bit floating-point and let the GPU shaders render as usual.

BTW, you have a choice --- you can simply translate the origin of the world coordinate-system to the camera position, but leave the axes alone, or you can transform the coordinate system so the axes of the camera become the axes of your new coordinate system. I prefer the former, largely because I support multiple cameras.

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OK, I understand that. But, I just tried to make a very large environment using a 1 unit to 1 metre scale... I drew a very large box (imagine drawing a box around Jupiter, 142984000 metres in each direction) and I had a camera that I could move around and moved forwards and backwards in very large steps too (millions of metres). What I found is that there were a lot of graphical glitches with bits of the box disappearing as I moved the camera around.

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Original post by Anessen
What I found is that there were a lot of graphical glitches with bits of the box disappearing as I moved the camera around.
That is caused by a lack of depth buffer precision, which is the next issue you have to deal with. Sean O'Neil has a post on the subject, which method I am using currently. Ysenaya and a few others had a neater solution using logarithmic depth buffers, which you should be able to find around GameDev.

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Original post by swiftcoder
Quote:
Original post by Anessen
What I found is that there were a lot of graphical glitches with bits of the box disappearing as I moved the camera around.
That is caused by a lack of depth buffer precision, which is the next issue you have to deal with. Sean O'Neil has a post on the subject, which method I am using currently. Ysenaya and a few others had a neater solution using logarithmic depth buffers, which you should be able to find around GameDev.
Note that recent GPUs and shader-languages support floating-point depth buffers. I believe this is more-or-less equivalent to logarithmic depth buffers, except floating-point depth buffers are now a built-in capability, and therefore requires NO special code in your program or shaders.

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Original post by maxgpgpu
Quote:
Original post by swiftcoder
Quote:
Original post by Anessen
What I found is that there were a lot of graphical glitches with bits of the box disappearing as I moved the camera around.
That is caused by a lack of depth buffer precision, which is the next issue you have to deal with. Sean O'Neil has a post on the subject, which method I am using currently. Ysenaya and a few others had a neater solution using logarithmic depth buffers, which you should be able to find around GameDev.
Note that recent GPUs and shader-languages support floating-point depth buffers. I believe this is more-or-less equivalent to logarithmic depth buffers, except floating-point depth buffers are now a built-in capability, and therefore requires NO special code in your program or shaders.


It doesn't matter if you're planning ahead or not - not everyone can or wants to upgrade. It's still a very good idea to provide something for those who won't be upgrading to the most recent hardware.

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Original post by maxgpgpu
Note that recent GPUs and shader-languages support floating-point depth buffers. I believe this is more-or-less equivalent to logarithmic depth buffers, except floating-point depth buffers are now a built-in capability, and therefore requires NO special code in your program or shaders.
I can't comment on that (although cameni agrees with you). However, I personally found that a floating point depth buffer was insufficient even for a planetary renderer (let alone the entire solar system), thus why I am using a variation on Sean O'Neil's method. I may revisit this decision at some point in the future, as floating-point depth buffers become more common.

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Original post by swiftcoderI can't comment on that (although cameni agrees with you). However, I personally found that a floating point depth buffer was insufficient even for a planetary renderer (let alone the entire solar system), thus why I am using a variation on Sean O'Neil's method. I may revisit this decision at some point in the future, as floating-point depth buffers become more common.
Actually I haven't tried the floating point depth buffer yet, but as I think about it now there still can be the same problem to some extent, for the large scale rendering. With the logarithmic Z-buffer all 32 bits are used, whereas the exponent of the floating point number is only 8 bits. The 1/Z curve is really unfriendly in this regard.

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We all assume f32 (single-precision) depth-buffers, not f16... correct?

Do remember, most objects that are extremely far away are single pixels, unless you intend to [figuratively speaking] look through 1000 power telescopes. When objects are so far away they are only 1 or 2 pixels in size, you really won't visually notice any z-buffer errors.

Now, some exceptions do exist, but the realities of astronomy tend to make them non-problematic. For example, the sun and jupiter are so large that they will still be several pixels in size even at large distances. So you could imagine looking at jupiter pass in front or behind the sun from neptune, for example, and both objects might be larger than 1 pixel. However, their distances are sooooo extremely different from each other, even with problematic resolution in the z-buffer, the "depth" of the sun and jupiter surely will not be the same... will they? Can you give a real-universe example of a problem that a simple f32 depth-buffer cannot handle correctly?

Have you tested f32 depth-buffers and actually visually SEEN a problem in the graphics rendering? If so, I would be inclined to sit myself down, work out the math for several approaches, and pay very close attention to their consequences.

I do not understand the point of "designing for older systems" however. Unless I am missing something, only moderately new GPU hardware supports fragment shaders that let you perform the depth decision-making explicitly AND lets you store, retrieve and test 32-bit integer depth values. Thus I don't see that limiting ourselves to "fairly up-to-date GPUs" can be avoided at all for our purposes.

One other option. The current generation of GPUs supports f64 variables and math, and f64 variables are supported in OpenCL and CUDA. So one other approach is to perform the depth computation in a supporting OpenCL function. Unfortunately, I haven't studied how annoying or difficult it is to mix shader code with OpenCL code - I only know it can be done, and works.

I suppose another solution might be to keep two depth buffers, one being the "upper 32-bits" of distance, and the other being the "lower 32-bits of distance". Obviously, one or both of these depth-buffers needs to be held in a framebuffer object, because the built-in methodologies do not seem to support two depth-buffers. I suppose, if we didn't need a stencil buffer (we wish), we could write fragment shader code to put 32-bits of depth information in the stencil buffer, and another 32-bits of depth information in the depth-buffer. OTOH, I don't see how that's more efficient than reading and writing additional depth information into attached framebuffers ala depth-info = gl_FragData[n] and gl_FragData[n] = depth-info.

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the simple solution which works on allhardware + requires no math is to draw things in 2(or more) phases

eg

clear depth
set z from 100km -> ~100,000 km
draw stuff here

clear depth buffer
set z from 10 -> ~110k meters
draw stuff here

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Original post by maxgpgpu
Now, some exceptions do exist, but the realities of astronomy tend to make them non-problematic. For example, the sun and jupiter are so large that they will still be several pixels in size even at large distances. So you could imagine looking at jupiter pass in front or behind the sun from neptune, for example, and both objects might be larger than 1 pixel. However, their distances are sooooo extremely different from each other, even with problematic resolution in the z-buffer, the "depth" of the sun and jupiter surely will not be the same... will they? Can you give a real-universe example of a problem that a simple f32 depth-buffer cannot handle correctly?
What you are saying would be perfectly true if the Z-buffer stored the depth value directly. The scales of things and distances when they are still visible would play nicely with the floating point depth. But instead it stores value of Z/W that has an abnormal resolution close to the near plane, but it falls down rapidly with distance.

Hmm, let's do a quick evaluation - for a scene like this: the near plane at 0.1m and the far plane at 300km (but that almost doesn't matter at all with the value of near plane). At 100km the Z/W value changes by 1e-10 per meter, at 10km the derivative is 1e-8. However, the problem here is that Z/W with rising Z approaches 1.0 (and not 0.0 where precision would be plenty), and the resolution of a 32b float around the value of 1.0 is somewhere around 1e-7, if I'm computing it right. That would make f32 depth buffer precision somewhere around 1km at that distance. Which is not what I'd expect from a floating point depth buffer at first thought [oh]

There might be something to be done about it though, as AFAIK the floating point depth values aren't clamped to 0..1, so it could be possible to set znear to a much larger value to reclaim the precision. If the clipping could be handled separately, somehow.

@zedz: yes, it looks simple, but having used it previously I must say that it is slower and/or there are problems at the boundaries, so one has to manage the terrain chunks and objects there. Can be done, but I wish there was a better and simpler solution with depth buffer.

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>>that it is slower

use

clear depoth
#A
glDepthRange(0,0.5);
#B
glDepthRange(0.5,1.0);

voila, no speedloss, what u are doing with Z/W will in fact result in a speed loss

>>there are problems at the boundaries
perhaps, but take your example 0.1m->300km.
now on earth u cant see anything 300km away typically due to curvature + haze, in the above picture of yours the furtherest mountain is ~10km

thus in such a scenario
A/ 0.1->20km // stuff on ground
B/ 10m->1000km // stuff in air

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Original post by zedz
>>there are problems at the boundaries
perhaps, but take your example 0.1m->300km. now on earth u cant see anything 300km away typically due to curvature + haze, in the above picture of yours the furtherest mountain is ~10km
I have the Sun and Moon visible from the surface of the Earth, which makes at least 2 depth layers, plus at least 2 more for the Earth itself - complexity starts to add up fast.

The bigger issue with the depth layering is that it doesn't interact well with deferred rendering, because you can't reconstruct position from depth at different layers. Planetary effects such as oceans and atmospheric scattering are considerably cheaper to render with deferred shading, so I can't really afford to switch back to a forward renderer just to work around depth layers.

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Original post by cameni
Quote:
Original post by maxgpgpu
Now, some exceptions do exist, but the realities of astronomy tend to make them non-problematic. For example, the sun and jupiter are so large that they will still be several pixels in size even at large distances. So you could imagine looking at jupiter pass in front or behind the sun from neptune, for example, and both objects might be larger than 1 pixel. However, their distances are sooooo extremely different from each other, even with problematic resolution in the z-buffer, the "depth" of the sun and jupiter surely will not be the same... will they? Can you give a real-universe example of a problem that a simple f32 depth-buffer cannot handle correctly?
What you are saying would be perfectly true if the Z-buffer stored the depth value directly. The scales of things and distances when they are still visible would play nicely with the floating point depth. But instead it stores value of Z/W that has an abnormal resolution close to the near plane, but it falls down rapidly with distance.

Hmm, let's do a quick evaluation - for a scene like this: the near plane at 0.1m and the far plane at 300km (but that almost doesn't matter at all with the value of near plane). At 100km the Z/W value changes by 1e-10 per meter, at 10km the derivative is 1e-8. However, the problem here is that Z/W with rising Z approaches 1.0 (and not 0.0 where precision would be plenty), and the resolution of a 32b float around the value of 1.0 is somewhere around 1e-7, if I'm computing it right. That would make f32 depth buffer precision somewhere around 1km at that distance. Which is not what I'd expect from a floating point depth buffer at first thought [oh]

There might be something to be done about it though, as AFAIK the floating point depth values aren't clamped to 0..1, so it could be possible to set znear to a much larger value to reclaim the precision. If the clipping could be handled separately, somehow.

Am I correct to infer that you are willing to require GPU cards that support vertex and fragment shaders? I assume so. Then why not perform Z-depth tests on straightforward distance values in floating point. In other words, forget Z/W... just perform depth tests based upon Z == distance.

If you have a relatively new GPU card, you can store Z distances in glFragDepth. If you have older GPU cards, you can attach a simple f32 monochrome framebuffer to glFragData[1] (or [2], or [3]), and write your Z distances in there. In fact, unless I'm forgetting something, you should be able to store an f32 Z-distance value into a 32-bit integer depth-buffer, as long as you configure OpenGL to not read/write/test that buffer itself (disable depth-buffering in OpenGL, and you explicitly read/write/test the buffer yourself in fragment shader code).

To speed up the process, you can eliminate the divide-by-W (if it actually requires a divide operation... not certain off hand) by performing the Z/W in the vertex shader and passing the Z-distance in an interpolating out variable. This way the fragment shader gets exact, interpolated Z-depth values without any need to perform a [relatively-slowish] divide operation. I do this trick in my vertex shaders for a different purpose (to pass normalized light->object vectors to the fragment shader, with true distances in the .w components).

In short, I suspect the best approach is to find a way to make the GPU perform Z-depth tests (not Z/W pseudo-depth tests) with f32 values.

Wait a second. Why not convert the transformed position.xyzw in the vertex shader to position.xyz1 (w component == 1.0000)? Then if your application has OpenGL create an f32 depth-buffer, the Z/W depth-test in hardware is the same as a Z depth-test. No?

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Original post by maxgpgpu
In short, I suspect the best approach is to find a way to make the GPU perform Z-depth tests (not Z/W pseudo-depth tests) with f32 values.

Wait a second. Why not convert the transformed position.xyzw in the vertex shader to position.xyz1 (w component == 1.0000)? Then if your application has OpenGL create an f32 depth-buffer, the Z/W depth-test in hardware is the same as a Z depth-test. No?
Well the problem is that the correct value of W is required because the rasterizer has to interpolate 1/W (and tex coords/W etc) to perform perspective correct texturing.

To get around that hardwired /W operation, value of Z can be premultiplied by W in the vertex shader, or, as you say, it can be written to glFragDepth in the pixel shader. Writing it in vertex shader leads to artifacts for polygons crossing the camera plane, where the 1/W changes rapidly. Using it in pixel shader with glFragDepth effectively disables fast-Z rejects, although this seems not to be a problem so far. Nevertheless, I'm using the vertex shader trick normally, and the pixel shader trick only on the objects close to the near camera plane.

However, unless there's something that can be done with the floating point depth buffer setup that would render these tricks in shaders unnecessary, I'll bet using the logarithmic depth buffer can give you a better precision due to better utilization of 32 bits.

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Quote:
Original post by zedz
clear depoth
#A
glDepthRange(0,0.5);
#B
glDepthRange(0.5,1.0);

voila, no speedloss, what u are doing with Z/W will in fact result in a speed loss

>>there are problems at the boundaries
perhaps, but take your example 0.1m->300km.
now on earth u cant see anything 300km away typically due to curvature + haze, in the above picture of yours the furtherest mountain is ~10km

thus in such a scenario
A/ 0.1->20km // stuff on ground
B/ 10m->1000km // stuff in air

Of course I have been using the depth range partitioning. But I was trying to say that it is slower when I have to do all the management. On the terrain I can see mountains as far as 150km (even more so now because the haze is unrealistically thin), so I have terrain tiles covering that whole range. I had to split the range 3 times for that, and could not use just the quadtree level to determine what tiles go where because the error metric would occasionally determine that a more distant tile but with larger features requires a refine, resulting in z-buffer artifacts because of the overlapping depth ranges. Then there's splitting the in-air objects, etc etc

All in all, using the logarithmic depth buffer showed to be much easier and elegant for me and others doing planetary rendering, even though it's not without problems.

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Wow.. these threads on "super huge rendering ranges!" always make me think.
Sure, there is the distinct case of planet rendering, where you want to go from the surface of a planet, out into space, over to another planet.
But on the surface of a world?
How far away IS the horizon? not 150Km for sure. Now, given that I've been bored more than once while driving between states, I'll say for sure that lots of valleys and tall mountains will give you places where you can see mountains 10-20miles before you get to them.

There is a big difference between having a world that is 150Km in size, and needing to render ALL of that as visible.

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Of course, that depends on what you are trying to do.
On the ground the visibility of mountains can be 20-30 miles at best, but from a plane at 14,000 feet you can see mountains 200 miles distant due to thinner air.
If you want an engine capable of this all you have to handle it somehow.

But that doesn't matter. Even at 10 miles you will have the problems with depth buffer. I thought floating point depth buffer would handle that. But it looks like it's adding precision where there was already plenty, and not helping much with the problematic distant part.

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So it looks the solution to the floating point depth buffer precision problem is easy. Swapping the values of far and near plane and changing the depth function to "greater" inverts the z/w shape so that it iterates towards zero with rising distance, where there is a plenty of resolution in the floating point.

I've also found an earlier post by Humus where he says the same thing, and also gives more insight into the old W-buffers and various Z-buffer properties and optimizations.

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      Resources (ITexture and IBuffer interfaces). There are two types of resources - textures and buffers. There are many different texture types (2D textures, 3D textures, texture array, cubmepas, etc.) that can all be represented by ITexture interface.
      Resources Views (ITextureView and IBufferView interfaces). While textures and buffers are mere data containers, texture views and buffer views describe how the data should be interpreted. For instance, a 2D texture can be used as a render target for rendering commands or as a shader resource.
      Pipeline State (IPipelineState interface). GPU pipeline contains many configurable stages (depth-stencil, rasterizer and blend states, different shader stage, etc.). Direct3D11 uses coarse-grain objects to set all stage parameters at once (for instance, a rasterizer object encompasses all rasterizer attributes), while OpenGL contains myriad functions to fine-grain control every individual attribute of every stage. Both methods do not map very well to modern graphics hardware that combines all states into one monolithic state under the hood. Direct3D12 directly exposes pipeline state object in the API, and Diligent Engine uses the same approach.
      Shader Resource Binding (IShaderResourceBinding interface). Shaders are programs that run on the GPU. Shaders may access various resources (textures and buffers), and setting correspondence between shader variables and actual resources is called resource binding. Resource binding implementation varies considerably between different API. Diligent Engine introduces a new object called shader resource binding that encompasses all resources needed by all shaders in a certain pipeline state.
      API Basics
      Creating Resources
      Device resources are created by the render device. The two main resource types are buffers, which represent linear memory, and textures, which use memory layouts optimized for fast filtering. Graphics APIs usually have a native object that represents linear buffer. Diligent Engine uses IBuffer interface as an abstraction for a native buffer. To create a buffer, one needs to populate BufferDesc structure and call IRenderDevice::CreateBuffer() method as in the following example:
      BufferDesc BuffDesc; BufferDesc.Name = "Uniform buffer"; BuffDesc.BindFlags = BIND_UNIFORM_BUFFER; BuffDesc.Usage = USAGE_DYNAMIC; BuffDesc.uiSizeInBytes = sizeof(ShaderConstants); BuffDesc.CPUAccessFlags = CPU_ACCESS_WRITE; m_pDevice->CreateBuffer( BuffDesc, BufferData(), &m_pConstantBuffer ); While there is usually just one buffer object, different APIs use very different approaches to represent textures. For instance, in Direct3D11, there are ID3D11Texture1D, ID3D11Texture2D, and ID3D11Texture3D objects. In OpenGL, there is individual object for every texture dimension (1D, 2D, 3D, Cube), which may be a texture array, which may also be multisampled (i.e. GL_TEXTURE_2D_MULTISAMPLE_ARRAY). As a result there are nine different GL texture types that Diligent Engine may create under the hood. In Direct3D12, there is only one resource interface. Diligent Engine hides all these details in ITexture interface. There is only one  IRenderDevice::CreateTexture() method that is capable of creating all texture types. Dimension, format, array size and all other parameters are specified by the members of the TextureDesc structure:
      TextureDesc TexDesc; TexDesc.Name = "My texture 2D"; TexDesc.Type = TEXTURE_TYPE_2D; TexDesc.Width = 1024; TexDesc.Height = 1024; TexDesc.Format = TEX_FORMAT_RGBA8_UNORM; TexDesc.Usage = USAGE_DEFAULT; TexDesc.BindFlags = BIND_SHADER_RESOURCE | BIND_RENDER_TARGET | BIND_UNORDERED_ACCESS; TexDesc.Name = "Sample 2D Texture"; m_pRenderDevice->CreateTexture( TexDesc, TextureData(), &m_pTestTex ); If native API supports multithreaded resource creation, textures and buffers can be created by multiple threads simultaneously.
      Interoperability with native API provides access to the native buffer/texture objects and also allows creating Diligent Engine objects from native handles. It allows applications seamlessly integrate native API-specific code with Diligent Engine.
      Next-generation APIs allow fine level-control over how resources are allocated. Diligent Engine does not currently expose this functionality, but it can be added by implementing IResourceAllocator interface that encapsulates specifics of resource allocation and providing this interface to CreateBuffer() or CreateTexture() methods. If null is provided, default allocator should be used.
      Initializing the Pipeline State
      As it was mentioned earlier, Diligent Engine follows next-gen APIs to configure the graphics/compute pipeline. One big Pipelines State Object (PSO) encompasses all required states (all shader stages, input layout description, depth stencil, rasterizer and blend state descriptions etc.). This approach maps directly to Direct3D12/Vulkan, but is also beneficial for older APIs as it eliminates pipeline misconfiguration errors. With many individual calls tweaking various GPU pipeline settings it is very easy to forget to set one of the states or assume the stage is already properly configured when in fact it is not. Using pipeline state object helps avoid these problems as all stages are configured at once.
      Creating Shaders
      While in earlier APIs shaders were bound separately, in the next-generation APIs as well as in Diligent Engine shaders are part of the pipeline state object. The biggest challenge when authoring shaders is that Direct3D and OpenGL/Vulkan use different shader languages (while Apple uses yet another language in their Metal API). Maintaining two versions of every shader is not an option for real applications and Diligent Engine implements shader source code converter that allows shaders authored in HLSL to be translated to GLSL. To create a shader, one needs to populate ShaderCreationAttribs structure. SourceLanguage member of this structure tells the system which language the shader is authored in:
      SHADER_SOURCE_LANGUAGE_DEFAULT - The shader source language matches the underlying graphics API: HLSL for Direct3D11/Direct3D12 mode, and GLSL for OpenGL and OpenGLES modes. SHADER_SOURCE_LANGUAGE_HLSL - The shader source is in HLSL. For OpenGL and OpenGLES modes, the source code will be converted to GLSL. SHADER_SOURCE_LANGUAGE_GLSL - The shader source is in GLSL. There is currently no GLSL to HLSL converter, so this value should only be used for OpenGL and OpenGLES modes. There are two ways to provide the shader source code. The first way is to use Source member. The second way is to provide a file path in FilePath member. Since the engine is entirely decoupled from the platform and the host file system is platform-dependent, the structure exposes pShaderSourceStreamFactory member that is intended to provide the engine access to the file system. If FilePath is provided, shader source factory must also be provided. If the shader source contains any #include directives, the source stream factory will also be used to load these files. The engine provides default implementation for every supported platform that should be sufficient in most cases. Custom implementation can be provided when needed.
      When sampling a texture in a shader, the texture sampler was traditionally specified as separate object that was bound to the pipeline at run time or set as part of the texture object itself. However, in most cases it is known beforehand what kind of sampler will be used in the shader. Next-generation APIs expose new type of sampler called static sampler that can be initialized directly in the pipeline state. Diligent Engine exposes this functionality: when creating a shader, textures can be assigned static samplers. If static sampler is assigned, it will always be used instead of the one initialized in the texture shader resource view. To initialize static samplers, prepare an array of StaticSamplerDesc structures and initialize StaticSamplers and NumStaticSamplers members. Static samplers are more efficient and it is highly recommended to use them whenever possible. On older APIs, static samplers are emulated via generic sampler objects.
      The following is an example of shader initialization:
      ShaderCreationAttribs Attrs; Attrs.Desc.Name = "MyPixelShader"; Attrs.FilePath = "MyShaderFile.fx"; Attrs.SearchDirectories = "shaders;shaders\\inc;"; Attrs.EntryPoint = "MyPixelShader"; Attrs.Desc.ShaderType = SHADER_TYPE_PIXEL; Attrs.SourceLanguage = SHADER_SOURCE_LANGUAGE_HLSL; BasicShaderSourceStreamFactory BasicSSSFactory(Attrs.SearchDirectories); Attrs.pShaderSourceStreamFactory = &BasicSSSFactory; ShaderVariableDesc ShaderVars[] = {     {"g_StaticTexture", SHADER_VARIABLE_TYPE_STATIC},     {"g_MutableTexture", SHADER_VARIABLE_TYPE_MUTABLE},     {"g_DynamicTexture", SHADER_VARIABLE_TYPE_DYNAMIC} }; Attrs.Desc.VariableDesc = ShaderVars; Attrs.Desc.NumVariables = _countof(ShaderVars); Attrs.Desc.DefaultVariableType = SHADER_VARIABLE_TYPE_STATIC; StaticSamplerDesc StaticSampler; StaticSampler.Desc.MinFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MagFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MipFilter = FILTER_TYPE_LINEAR; StaticSampler.TextureName = "g_MutableTexture"; Attrs.Desc.NumStaticSamplers = 1; Attrs.Desc.StaticSamplers = &StaticSampler; ShaderMacroHelper Macros; Macros.AddShaderMacro("USE_SHADOWS", 1); Macros.AddShaderMacro("NUM_SHADOW_SAMPLES", 4); Macros.Finalize(); Attrs.Macros = Macros; RefCntAutoPtr<IShader> pShader; m_pDevice->CreateShader( Attrs, &pShader );
      Creating the Pipeline State Object
      After all required shaders are created, the rest of the fields of the PipelineStateDesc structure provide depth-stencil, rasterizer, and blend state descriptions, the number and format of render targets, input layout format, etc. For instance, rasterizer state can be described as follows:
      PipelineStateDesc PSODesc; RasterizerStateDesc &RasterizerDesc = PSODesc.GraphicsPipeline.RasterizerDesc; RasterizerDesc.FillMode = FILL_MODE_SOLID; RasterizerDesc.CullMode = CULL_MODE_NONE; RasterizerDesc.FrontCounterClockwise = True; RasterizerDesc.ScissorEnable = True; RasterizerDesc.AntialiasedLineEnable = False; Depth-stencil and blend states are defined in a similar fashion.
      Another important thing that pipeline state object encompasses is the input layout description that defines how inputs to the vertex shader, which is the very first shader stage, should be read from the memory. Input layout may define several vertex streams that contain values of different formats and sizes:
      // Define input layout InputLayoutDesc &Layout = PSODesc.GraphicsPipeline.InputLayout; LayoutElement TextLayoutElems[] = {     LayoutElement( 0, 0, 3, VT_FLOAT32, False ),     LayoutElement( 1, 0, 4, VT_UINT8, True ),     LayoutElement( 2, 0, 2, VT_FLOAT32, False ), }; Layout.LayoutElements = TextLayoutElems; Layout.NumElements = _countof( TextLayoutElems ); Finally, pipeline state defines primitive topology type. When all required members are initialized, a pipeline state object can be created by IRenderDevice::CreatePipelineState() method:
      // Define shader and primitive topology PSODesc.GraphicsPipeline.PrimitiveTopologyType = PRIMITIVE_TOPOLOGY_TYPE_TRIANGLE; PSODesc.GraphicsPipeline.pVS = pVertexShader; PSODesc.GraphicsPipeline.pPS = pPixelShader; PSODesc.Name = "My pipeline state"; m_pDev->CreatePipelineState(PSODesc, &m_pPSO); When PSO object is bound to the pipeline, the engine invokes all API-specific commands to set all states specified by the object. In case of Direct3D12 this maps directly to setting the D3D12 PSO object. In case of Direct3D11, this involves setting individual state objects (such as rasterizer and blend states), shaders, input layout etc. In case of OpenGL, this requires a number of fine-grain state tweaking calls. Diligent Engine keeps track of currently bound states and only calls functions to update these states that have actually changed.
      Binding Shader Resources
      Direct3D11 and OpenGL utilize fine-grain resource binding models, where an application binds individual buffers and textures to certain shader or program resource binding slots. Direct3D12 uses a very different approach, where resource descriptors are grouped into tables, and an application can bind all resources in the table at once by setting the table in the command list. Resource binding model in Diligent Engine is designed to leverage this new method. It introduces a new object called shader resource binding that encapsulates all resource bindings required for all shaders in a certain pipeline state. It also introduces the classification of shader variables based on the frequency of expected change that helps the engine group them into tables under the hood:
      Static variables (SHADER_VARIABLE_TYPE_STATIC) are variables that are expected to be set only once. They may not be changed once a resource is bound to the variable. Such variables are intended to hold global constants such as camera attributes or global light attributes constant buffers. Mutable variables (SHADER_VARIABLE_TYPE_MUTABLE) define resources that are expected to change on a per-material frequency. Examples may include diffuse textures, normal maps etc. Dynamic variables (SHADER_VARIABLE_TYPE_DYNAMIC) are expected to change frequently and randomly. Shader variable type must be specified during shader creation by populating an array of ShaderVariableDesc structures and initializing ShaderCreationAttribs::Desc::VariableDesc and ShaderCreationAttribs::Desc::NumVariables members (see example of shader creation above).
      Static variables cannot be changed once a resource is bound to the variable. They are bound directly to the shader object. For instance, a shadow map texture is not expected to change after it is created, so it can be bound directly to the shader:
      PixelShader->GetShaderVariable( "g_tex2DShadowMap" )->Set( pShadowMapSRV ); Mutable and dynamic variables are bound via a new Shader Resource Binding object (SRB) that is created by the pipeline state (IPipelineState::CreateShaderResourceBinding()):
      m_pPSO->CreateShaderResourceBinding(&m_pSRB); Note that an SRB is only compatible with the pipeline state it was created from. SRB object inherits all static bindings from shaders in the pipeline, but is not allowed to change them.
      Mutable resources can only be set once for every instance of a shader resource binding. Such resources are intended to define specific material properties. For instance, a diffuse texture for a specific material is not expected to change once the material is defined and can be set right after the SRB object has been created:
      m_pSRB->GetVariable(SHADER_TYPE_PIXEL, "tex2DDiffuse")->Set(pDiffuseTexSRV); In some cases it is necessary to bind a new resource to a variable every time a draw command is invoked. Such variables should be labeled as dynamic, which will allow setting them multiple times through the same SRB object:
      m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "cbRandomAttribs")->Set(pRandomAttrsCB); Under the hood, the engine pre-allocates descriptor tables for static and mutable resources when an SRB objcet is created. Space for dynamic resources is dynamically allocated at run time. Static and mutable resources are thus more efficient and should be used whenever possible.
      As you can see, Diligent Engine does not expose low-level details of how resources are bound to shader variables. One reason for this is that these details are very different for various APIs. The other reason is that using low-level binding methods is extremely error-prone: it is very easy to forget to bind some resource, or bind incorrect resource such as bind a buffer to the variable that is in fact a texture, especially during shader development when everything changes fast. Diligent Engine instead relies on shader reflection system to automatically query the list of all shader variables. Grouping variables based on three types mentioned above allows the engine to create optimized layout and take heavy lifting of matching resources to API-specific resource location, register or descriptor in the table.
      This post gives more details about the resource binding model in Diligent Engine.
      Setting the Pipeline State and Committing Shader Resources
      Before any draw or compute command can be invoked, the pipeline state needs to be bound to the context:
      m_pContext->SetPipelineState(m_pPSO); Under the hood, the engine sets the internal PSO object in the command list or calls all the required native API functions to properly configure all pipeline stages.
      The next step is to bind all required shader resources to the GPU pipeline, which is accomplished by IDeviceContext::CommitShaderResources() method:
      m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES); The method takes a pointer to the shader resource binding object and makes all resources the object holds available for the shaders. In the case of D3D12, this only requires setting appropriate descriptor tables in the command list. For older APIs, this typically requires setting all resources individually.
      Next-generation APIs require the application to track the state of every resource and explicitly inform the system about all state transitions. For instance, if a texture was used as render target before, while the next draw command is going to use it as shader resource, a transition barrier needs to be executed. Diligent Engine does the heavy lifting of state tracking.  When CommitShaderResources() method is called with COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES flag, the engine commits and transitions resources to correct states at the same time. Note that transitioning resources does introduce some overhead. The engine tracks state of every resource and it will not issue the barrier if the state is already correct. But checking resource state is an overhead that can sometimes be avoided. The engine provides IDeviceContext::TransitionShaderResources() method that only transitions resources:
      m_pContext->TransitionShaderResources(m_pPSO, m_pSRB); In some scenarios it is more efficient to transition resources once and then only commit them.
      Invoking Draw Command
      The final step is to set states that are not part of the PSO, such as render targets, vertex and index buffers. Diligent Engine uses Direct3D11-syle API that is translated to other native API calls under the hood:
      ITextureView *pRTVs[] = {m_pRTV}; m_pContext->SetRenderTargets(_countof( pRTVs ), pRTVs, m_pDSV); // Clear render target and depth buffer const float zero[4] = {0, 0, 0, 0}; m_pContext->ClearRenderTarget(nullptr, zero); m_pContext->ClearDepthStencil(nullptr, CLEAR_DEPTH_FLAG, 1.f); // Set vertex and index buffers IBuffer *buffer[] = {m_pVertexBuffer}; Uint32 offsets[] = {0}; Uint32 strides[] = {sizeof(MyVertex)}; m_pContext->SetVertexBuffers(0, 1, buffer, strides, offsets, SET_VERTEX_BUFFERS_FLAG_RESET); m_pContext->SetIndexBuffer(m_pIndexBuffer, 0); Different native APIs use various set of function to execute draw commands depending on command details (if the command is indexed, instanced or both, what offsets in the source buffers are used etc.). For instance, there are 5 draw commands in Direct3D11 and more than 9 commands in OpenGL with something like glDrawElementsInstancedBaseVertexBaseInstance not uncommon. Diligent Engine hides all details with single IDeviceContext::Draw() method that takes takes DrawAttribs structure as an argument. The structure members define all attributes required to perform the command (primitive topology, number of vertices or indices, if draw call is indexed or not, if draw call is instanced or not, if draw call is indirect or not, etc.). For example:
      DrawAttribs attrs; attrs.IsIndexed = true; attrs.IndexType = VT_UINT16; attrs.NumIndices = 36; attrs.Topology = PRIMITIVE_TOPOLOGY_TRIANGLE_LIST; pContext->Draw(attrs); For compute commands, there is IDeviceContext::DispatchCompute() method that takes DispatchComputeAttribs structure that defines compute grid dimension.
      Source Code
      Full engine source code is available on GitHub and is free to use. The repository contains two samples, asteroids performance benchmark and example Unity project that uses Diligent Engine in native plugin.
      AntTweakBar sample is Diligent Engine’s “Hello World” example.

       
      Atmospheric scattering sample is a more advanced example. It demonstrates how Diligent Engine can be used to implement various rendering tasks: loading textures from files, using complex shaders, rendering to multiple render targets, using compute shaders and unordered access views, etc.

      Asteroids performance benchmark is based on this demo developed by Intel. It renders 50,000 unique textured asteroids and allows comparing performance of Direct3D11 and Direct3D12 implementations. Every asteroid is a combination of one of 1000 unique meshes and one of 10 unique textures.

      Finally, there is an example project that shows how Diligent Engine can be integrated with Unity.

      Future Work
      The engine is under active development. It currently supports Windows desktop, Universal Windows and Android platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and support for more platforms is planned.
    • By reenigne
      For those that don't know me. I am the individual who's two videos are listed here under setup for https://wiki.libsdl.org/Tutorials
      I also run grhmedia.com where I host the projects and code for the tutorials I have online.
      Recently, I received a notice from youtube they will be implementing their new policy in protecting video content as of which I won't be monetized till I meat there required number of viewers and views each month.

      Frankly, I'm pretty sick of youtube. I put up a video and someone else learns from it and puts up another video and because of the way youtube does their placement they end up with more views.
      Even guys that clearly post false information such as one individual who said GLEW 2.0 was broken because he didn't know how to compile it. He in short didn't know how to modify the script he used because he didn't understand make files and how the requirements of the compiler and library changes needed some different flags.

      At the end of the month when they implement this I will take down the content and host on my own server purely and it will be a paid system and or patreon. 

      I get my videos may be a bit dry, I generally figure people are there to learn how to do something and I rather not waste their time. 
      I used to also help people for free even those coming from the other videos. That won't be the case any more. I used to just take anyone emails and work with them my email is posted on the site.

      I don't expect to get the required number of subscribers in that time or increased views. Even if I did well it wouldn't take care of each reoccurring month.
      I figure this is simpler and I don't plan on putting some sort of exorbitant fee for a monthly subscription or the like.
      I was thinking on the lines of a few dollars 1,2, and 3 and the larger subscription gets you assistance with the content in the tutorials if needed that month.
      Maybe another fee if it is related but not directly in the content. 
      The fees would serve to cut down on the number of people who ask for help and maybe encourage some of the people to actually pay attention to what is said rather than do their own thing. That actually turns out to be 90% of the issues. I spent 6 hours helping one individual last week I must have asked him 20 times did you do exactly like I said in the video even pointed directly to the section. When he finally sent me a copy of the what he entered I knew then and there he had not. I circled it and I pointed out that wasn't what I said to do in the video. I didn't tell him what was wrong and how I knew that way he would go back and actually follow what it said to do. He then reported it worked. Yea, no kidding following directions works. But hey isn't alone and well its part of the learning process.

      So the point of this isn't to be a gripe session. I'm just looking for a bit of feed back. Do you think the fees are unreasonable?
      Should I keep the youtube channel and do just the fees with patreon or do you think locking the content to my site and require a subscription is an idea.

      I'm just looking at the fact it is unrealistic to think youtube/google will actually get stuff right or that youtube viewers will actually bother to start looking for more accurate videos. 
    • By Balma Alparisi
      i got error 1282 in my code.
      sf::ContextSettings settings; settings.majorVersion = 4; settings.minorVersion = 5; settings.attributeFlags = settings.Core; sf::Window window; window.create(sf::VideoMode(1600, 900), "Texture Unit Rectangle", sf::Style::Close, settings); window.setActive(true); window.setVerticalSyncEnabled(true); glewInit(); GLuint shaderProgram = createShaderProgram("FX/Rectangle.vss", "FX/Rectangle.fss"); float vertex[] = { -0.5f,0.5f,0.0f, 0.0f,0.0f, -0.5f,-0.5f,0.0f, 0.0f,1.0f, 0.5f,0.5f,0.0f, 1.0f,0.0f, 0.5,-0.5f,0.0f, 1.0f,1.0f, }; GLuint indices[] = { 0,1,2, 1,2,3, }; GLuint vao; glGenVertexArrays(1, &vao); glBindVertexArray(vao); GLuint vbo; glGenBuffers(1, &vbo); glBindBuffer(GL_ARRAY_BUFFER, vbo); glBufferData(GL_ARRAY_BUFFER, sizeof(vertex), vertex, GL_STATIC_DRAW); GLuint ebo; glGenBuffers(1, &ebo); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices,GL_STATIC_DRAW); glVertexAttribPointer(0, 3, GL_FLOAT, false, sizeof(float) * 5, (void*)0); glEnableVertexAttribArray(0); glVertexAttribPointer(1, 2, GL_FLOAT, false, sizeof(float) * 5, (void*)(sizeof(float) * 3)); glEnableVertexAttribArray(1); GLuint texture[2]; glGenTextures(2, texture); glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture[0]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); sf::Image* imageOne = new sf::Image; bool isImageOneLoaded = imageOne->loadFromFile("Texture/container.jpg"); if (isImageOneLoaded) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageOne->getSize().x, imageOne->getSize().y, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageOne->getPixelsPtr()); glGenerateMipmap(GL_TEXTURE_2D); } delete imageOne; glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[1]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); sf::Image* imageTwo = new sf::Image; bool isImageTwoLoaded = imageTwo->loadFromFile("Texture/awesomeface.png"); if (isImageTwoLoaded) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageTwo->getSize().x, imageTwo->getSize().y, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageTwo->getPixelsPtr()); glGenerateMipmap(GL_TEXTURE_2D); } delete imageTwo; glUniform1i(glGetUniformLocation(shaderProgram, "inTextureOne"), 0); glUniform1i(glGetUniformLocation(shaderProgram, "inTextureTwo"), 1); GLenum error = glGetError(); std::cout << error << std::endl; sf::Event event; bool isRunning = true; while (isRunning) { while (window.pollEvent(event)) { if (event.type == event.Closed) { isRunning = false; } } glClear(GL_COLOR_BUFFER_BIT); if (isImageOneLoaded && isImageTwoLoaded) { glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture[0]); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[1]); glUseProgram(shaderProgram); } glBindVertexArray(vao); glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, nullptr); glBindVertexArray(0); window.display(); } glDeleteVertexArrays(1, &vao); glDeleteBuffers(1, &vbo); glDeleteBuffers(1, &ebo); glDeleteProgram(shaderProgram); glDeleteTextures(2,texture); return 0; } and this is the vertex shader
      #version 450 core layout(location=0) in vec3 inPos; layout(location=1) in vec2 inTexCoord; out vec2 TexCoord; void main() { gl_Position=vec4(inPos,1.0); TexCoord=inTexCoord; } and the fragment shader
      #version 450 core in vec2 TexCoord; uniform sampler2D inTextureOne; uniform sampler2D inTextureTwo; out vec4 FragmentColor; void main() { FragmentColor=mix(texture(inTextureOne,TexCoord),texture(inTextureTwo,TexCoord),0.2); } I was expecting awesomeface.png on top of container.jpg

    • By khawk
      We've just released all of the source code for the NeHe OpenGL lessons on our Github page at https://github.com/gamedev-net/nehe-opengl. code - 43 total platforms, configurations, and languages are included.
      Now operated by GameDev.net, NeHe is located at http://nehe.gamedev.net where it has been a valuable resource for developers wanting to learn OpenGL and graphics programming.

      View full story
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