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OpenGL Fast Way To Determine If All Pixels In Opengl Depth Buffer Were Drawn At Least Once?

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Hello, I am programming a FPS game and I simply want to make it faster. I tried a lot of things, from which few of them worked. My testing map has 15k vertexes and 26k triangles, and I am using partitioning space by X*Y*Z orthogonal cubes. Thats fine cause it works. Next thing that helped a lot was to order partitions by metric from partition where I am and display them from nearest, which caused OpenGl to not overdraw it so much. Also I use face culling and my own per-triangle frustum clipping, and also overdraw check that makes it sure that same triangle is rendered only once. Also before loading a map, the triangle lists of each partition are ordered by texture to minimalize need of switching glEnd and glBegin, which caused big slowdown. Also, I tried arranging triangles into triangle strips, but they suck arse, and also I tried using VBOs instead glBegin and glEnd, but it didnt helped that much as internet promised. My next, yet undone idea is to compute all this stuff just when the player position and rotation changes, and if not just render it as before without any computations.


Anyway, in every tic I count number of triangles being actually drawn. As a testing map I use Hell Gate from Quake III (that one with crazy mouth in a room, if somebody knows that one :D ) loaded from exported .obj file. When I am on the end of map and looking outside (in the mouth), 36 triangles are being drawn, which seems fair to me. However, turning by 180 degrees causes me to look INSIDE the map and my frustum to contain nearly all partitions, and 22k triangles from 26k are displayed. Now I get to my idea - display few partitions, then CHECK IF ALL PIXELS WERE DISPLAYED, if not, display some more partitions, and so on. That could make it really fast, cause it would cut of everything excpet the first room. Problém is that extracting depth buffer and checking all the 1920x1080 of that little guys is so slow that it would be contraproductive (proven by try).


So my question is - is there actually a FAST way how to check if all pixels are rendered at least once? (= if the depth value is not 127 anywhere) I did like 3-hours research which didnt found answer. Also, if people here will say "no" it will encourage me in writing my own rasterization (at least I will have totally full control).

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There's a hardware feature called 'occlusion queries', which do exactly what you're looking for -- determine a yes/no answer to whether something was drawn or not. To find out if there's "holes" in the depth buffer, you can draw a quad that's very far away using an occlusion query, and check if the result is "yes - the quad was visible".

Now I get to my idea - display few partitions, then CHECK IF ALL PIXELS WERE DISPLAYED, if not, display some more partitions, and so on. That could make it really fast, cause it would cut of everything excpet the first room. Problém is that extracting depth buffer and checking all the 1920x1080 of that little guys is so slow that it would be contraproductive (proven by try).

 A bigger problem is that the CPU and GPU have a very large latency between them. When you call any glDraw function, the driver is actually writing a command packet into a queue (like networking!), and the GPU might not execute that command until, say, 30ms later. This is perfectly fine in most situations, as the CPU and GPU form a pipeline with huge throughput, but long latency.
e.g. a healthy timeline looks like:

CPU: | Frame 1 | Frame 2 | Frame 3 | ...
GPU: | wait    | Frame 1 | Frame 2 | ...

If you ever try to read GPU data back to the CPU during a frame -- e.g. you split your frame into two parts (A/B) with a read-back operation in between them, you end up with a timeline like this:

CPU: | Frame1.A | wait      |Copy| Frame1.B | Frame2.A | wait      |Copy| Frame2.B | Frame3.A | ...
GPU: | wait     | Frame 1.A |Copy| wait     | Frame1.B | Frame 2.A |Copy| wait     | Frame2.B | ...

Now, both the CPU and GPU spend roughly half of the time idle, waiting on the other processor.
If you're going to read back GPU data, you need to wait at least one frame before requesting the results, to avoid causing a pipeline bubble :(
That means that reading back GPU data to use in CPU-driven occlusion culling is a dead-end for performance.

Edited by Hodgman

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Writing your own rasterizer isn't really going to solve your problem, since you won't be utilizing your GPU at all (or if you use compute, not as efficiently as you could be). Just leave that stuff to the GPU guys, they know what they're doing. :)


Anyway, do you really need such precise culling? I mean, are you absolutely sure you're GPU bound? Going into such detail just to cull a few triangles might not be worth it, and could hurt your performance rather than help if you're actually CPU bound since modern GPUs prefer to eat big chunks of data more than they like to issue a draw call for each individual triangle. If you have bounding box culling on your objects, and frustum culling, then I think that's all you'll really need unless you're writing a big AAA title with a very high scene complexity.


Just bear in mind that Quake levels were built for some different hardware constraints, so you should probably break up the obj model you have into small sections to avoid processing the entire mesh in one chunk so that you can leverage those two culling systems a little more.


That said, if you really want to have some proper occlusion culling for triangles, you can either check out the Frostbite approach (it's quite complicated iirc), or try implementing a simple Hi-Z culling system using Geometry Shaders (build a simple quad-tree out of your zbuffer and do quad-based culling on each triangle using the geometry shader). The later is simpler to implement and I've had pretty good results with it.

Edited by Styves

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So I tried occlusion culling. Principially it works, but guess what. :D


It made it slower. Initially I got framerate 42. When I try to do test of gl_samples count every 20 partitions = 38 fps. Every 10 partitions = 32 fps :(

Making list of displayed triangles in previous frame helped, when I dont move - I get 41, but when I move, it for sure drops on 32.

And yes I think it is worth, cause I see like 5k triangles max. When I have to pass 15k triangles to OpenGl more, it is very noobish performance leak.

Anyway thank you guys.

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"Thousands of triangles" should not be something that alters the framerate so dramatically. A modern game can draw hundreds of thousands of triangles at 1000fps -- which is one of the reasons that VBO's replaced begin/end (same number of gl function calls required for any number of triangles).


You need to profile your game to find out where the time is being spent. Set up a class that records the high-frequency timer at two points in time, subtracts the difference, and logs the result, and then put instances of this class in any function that you think might be a performance hog.

It's common to do this with a constructor/destructor:

struct ProfileLogger { ProfileLogger(const char* name) { PushProfileScope(name); } ~ProfileLogger() { PopProfileScope(); } };
#define Profile(name) ProfileLogger _profile_(name);
void Test()
  Profile("Test");// calls PushProfileScope("Test") here
}// calls PopProfileScope("Test") here

From this data you can get a hierarchical breakdown of where all your CPU time is spent per frame. Trying to optimize without this data is just shooting in the dark.


From the sounds of it, your game is almost certainly CPU-bound, so you can start here. Later on though, you can use gl timer queries to do the same thing on the GPU side -- wrapping parts of the scene in two timer queries to find out how long it took the GPU to process those commands.

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Displaying is the actual bottleneck, cause I have done this stuff before. What I didnt knew was that on testing computer there was Nvidia set to best antialiasing and texture filtering, so I turned them off and now it runs stably on 60fps without any visible change to worse :)


... anyway, if the occlusion culling queries are so slow, what is their point then? Will for example GL_ANY_SAMPLES_PASSED_CONSERVATIVE speed it up? Another idea is lowering viewport resolution when doing queries and then setting it back to normal ...

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The problem with this use of occlusion queries is the pipeline bubble caused by reading back results on the same frame. Even if the query itself is free, this bubble will halve your framerate.


Reading back an occlusion query is fine if you wait one frame before requesting the result, as this won't disrupt the pipeline. This is useful for things like lens flares or special effects where you don't care about the data being one frame old, but is dangerous for deciding what parts of the scene to draw :(

Generally they're a pretty useless API feature...


In a modern engine though, you can move all your culling and "what to draw" code off the CPU and into a compute shader. You can then issue draw-indirect commands to say "you will be drawing something, but I don't know which triangles, yet. The number and offset will be present in this buffer later (which is filled in by the compute shader).


For something like a quake3 level though, you should be able to have a constant draw cost regardless of how many triangles are visible. The level triangle data is static, so put it in a VBO once and never update it again.

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That Hi-Z culling looks promising, I will leave it as a backup idea for optimization. I dont doubt that lighting model will fuck up the framerate significantly when I will do it, so there for sure will be need for any optimizing stuff that works. But since I have already 60fps now and people around me demand mainly the basic functionality ("How its going with a game?" "I made it faster" "And can I play it?" "Not yet"), I must move on networking and multiplayer ASAP.


By the way I dont think that constant draw cost is good. I could measure time of the loop and if some time will remain, then do some filler work like pre-loading chunk of next map to second map buffer or something :)

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Since you're using a Quake 3 map, the classic Quake method of solving this was to precompute a potentially visible set (or PVS) using an offline pre-processor, then do checks against that PVS at runtime to determine what should (or should not) be drawn.


In (very basic) outline, you divide your map into what I'll call "areas"; these could be nodes/leafs in a BSP tree (which was what Quake used), rooms, cubes in a grid, whatever.  Then for each such area, you use some brute-force method to determine what other areas are potentially visible from it (I believe that the "potentially" part is on account of some coarseness in the algorithm, as well as the fact that this stage ignores frustum culling which is still done at runtime).  Store out the result in some fast and compact data format (Quake used a bitfield array).  Then at runtime you're just looking up those stored results, draw calls, overdraw, etc all go down, the map runs faster, and everbody is happy.


The downside is that the pre-processing can take time, needs to be re-run even if you make trivial changes to your map, and needs a custom map format to store the data.  And while we're on the subject of formats, .obj is a horrible, horrible, horrible, horrible, horrible format to use for game maps.  The only reason to use it is if you really love writing text parsers.  The ideal format is where you memory-map a file, read some headers to set up some sizes, then glBufferData the rest.  Simple, quick to load, no faffing about.  And while we're on the subject of glBufferData, if your observation is that VBOs are slower than glBegin/glEnd, then you're using them wrong: probably by writing a glBegin/glEnd-alike wrapper around the VBO API.

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You understood me bad - I am loading from .obj just initially after I model some thing in Cinema4D and export it. Then I have a function in my engine that already saves a map in my own format, which saves every number as bytes, plus there is also space partitioning saved in that file. I dont know what exactly you mean with memory-mapping a file, but from name it sounds that it would only work for static arrays of classes, and not for linear linked list of dynamically allocated classes as I have. I like .obj cause its intuitive and readable and there is no reverse engineering about format specification.


PVS are really good idea, I like it. I will definitely try it. I am thinking of making special class for that, which is some box area and list of other box areas that are potentially visible. In map editor, the user will choose these manually so there will be no need to make some extra complicated code that determines what is visible from where (even if THIS is exactly the point where occlussion culling would be useful...) and also no need to compile a map like this after every change.

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My testing map has 15k vertexes and 26k triangles, and I am using


You are looking for optimizations in the wrong place if you are getting such low framerates, with or without any texture filtering. This scene is on my old Radeon 7870 video card from 3 years ago:


This is 3,000 plants drawn on top of a terrain with anisotropic texture filtering set to highest, or at least medium. So we are talking about 1 million triangles and plenty of overdraw between the plants. FPS was ... I don't remember around 60 though. You have other issues to sort out depending on how good your hardware is. 30 FPS is bad. 60fps sounds like you may have vsync on so it is capping it at 60. Typically vsync will cap framerates to either 30 or 60, nothing in between. At 56 fps you could be capped down to 30 potentially.



Edited by dpadam450

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Comp where it was tested is Asus X751L. Has Nvidia GeForce 820M, Intel Core i7-4500U 1.8GHz, 12GB RAM. I think hardware should be enough OK.

And yes I am using vsync, thats why I get 60fps. Previously I heard that 25fps is OK, but truth is that you feel subliminaly that something is wrong. I choose 60fps. The texture of triangles was just 32x32. When I put there some 256x256 texture, framerate is same (so there is so far no need for mipmapping).


Your image looks nice, I even see you have some shadows. Perhaps I could make similar benchtest like that and test on it.

I got next idea that I will implement some multithreading (theoretically less then 4x speedup when done correctly). Do you guys use it in your games?

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I choose 60fps. The texture of triangles was just 32x32. When I put there some 256x256 texture, framerate is same (so there is so far no need for mipmapping).


Any other good reasons for this ? Actually you might not see any differences, but maybe later, you will notice a performance drop, and you'll spend days (and certainly a lot more) to detect that this is due to the fact that you don't use mipmapping. One big reason for this is that you currently use vsync. So as long as your GPU can afford things, you'll have 60 fps, but once it won't, you won't get 59 fps or so, you'll end up with 30 fps...

Mipmaps is just a factor of few more lines in your code.

Of course, it (almost) double the memory requirement for all your images. But except if you really target to use most of your VRAM for your geometry (and other buffers), I don't see any real good motivations by not using mipmapping.

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Mipmapping is not only a performance thing; it's also affects image quality, and in fact the primary reason why mipmapping was invented in the first place was for quality.





They are intended to increase rendering speed and reduce aliasing artifacts. .....  Mipmapping was invented by Lance Williams in 1983 and is described in his paper Pyramidal parametrics. From the abstract: "This paper advances a 'pyramidal parametric' prefiltering and sampling geometry which minimizes aliasing effects and assures continuity within and between target images." The "pyramid" can be imagined as the set of mipmaps stacked on top of each other.


I suggest that you do some research on aliasing to fully understand the problems that this solves.  Also be aware that to some people, aliasing may be confused with additional detail.


Mipmaps don't use almost double the memory - they use one-third extra.  But don't get fooled into thinking that memory usage is a primary arbiter of performance, because it's not.

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Mipmapping is not only a performance thing; it's also affects image quality


Right. But one could notice aliasing effects more easily. Aliasing on a textured object could probably means a texture issue (or depth issue, right). But a sudden FPS drop can have many reasons.


Mipmaps don't use almost double the memory - they use one-third extra.


Right too. I'm still wondering how I could reach such a result...

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How much faster should be VBO compared to glBegin/glEnd?


Cause with glBegin/glEnd I got 41fps and with VBO like 43fps in same point. So yes, it IS faster, but honestly I expected more improvement, since its one of main tips people give you on optimization of displaying. The speedup will probably vary depending on type of rendered stuff, but I dont know where it helps most. Another 2 problems (minor problems, I can survive these) is ugly syntax compared to glBegin/End and fact that when you create VBO for some object that changes geometry, the VBO doesnt change with position of vertexes, so you must reupdate positions that are previously copied into the data buffer.

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the VBO doesnt change with position of vertexes, so you must reupdate positions that are previously copied into the data buffer.


The best thing, as far as you can do it, is to let the vertex shader do these calculations.


How much faster should be VBO compared to glBegin/glEnd?


It depends on many things. And this might be related to the fact that you update the VBO each frame with new vertex positions.


If you want/can live with GL immediate mode, then why not. But you must be aware that immediate mode is deprecated since GL 3. For example your code won't work on Apple machines, and on mobile devices neither.

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How much faster should be VBO compared to glBegin/glEnd?
Cause with glBegin/glEnd I got 41fps and with VBO like 43fps in same point. So yes, it IS faster, but honestly I expected more improvement...

This is the naive expectation.  As Silence correctly observes, if your VBO implementation is just a glBegin/glEnd-like wrapper around the VBO API, or if you're updating data each frame, glBegin/glEnd will often outperform it.  It's common to see bad VBO usage actually perform worse.  An alternative for the dynamic data requirement is to use client-side vertex arrays.


It's also the case that your actual bottleneck may be elsewhere.  GPU pipelines are very deep and using a VBO just addresses performance at one very small part of them.  If you're not actually transferring much data to the GPU (and 15k vertices is not much) then using a VBO, even in the best case scnario, isn't going to give you much perf gain, if any.

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Recently I have done the networking and tested it by first deathmatch ever. But the performance on other comps than mine is still one of big problems. I figured out, that when I replace item models with simplified ones, I get OK fps, but thats a wimpy solution.

Also - mipmaps have been implemented. Adjustable LOD bias has no effect on performance, even if set as high (like 9) that textures fade into single color.

It is sow really in glBegin/glEnd when switching textures. Texture sorting helped a bit, but not totally. So I packed all my textures to one big, and before compiling a map i will do just linear fix for texcoords to make their xy ranges in big texture. Trouble is that it will not repeat or wrap anymore, and I need that. Texcoords outside 0..1 will continue in big map through other textures, which is what I dont want. I was looking on Internet for solutions, but there is nothing. My idea is to somehow get into place in memory where texture is stored and manually hack width and height and starting pointer, to make it think that its actually just a region of itself. There will be complication with mipmaps, but thats not the immediate problem. Also textures will have to be stored not in image as I see it, but lineary after rows, so program could read it. I have dilema if I should go for it or no, cause maybe there is function like that - I just looked not enough. Anyone knows a functions that draws only region of texture? I care only about those WITH PRESERVED ABILITY TO WRAP OR REPEAT - the answer TexCoord2f(0.5,0.5) really is not what I am looking for :D

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      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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