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OpenGL Hypothesizing a new lighting method.

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Hi Everybody. This is my first post so please be nice. I'm new to graphics programming with OpenGL and have only done basic tutorials thus far.

 

After going through the deferred rendering tutorial at http://ogldev.atspace.co.uk/, I was kind of left with the impression that the process of deferred lighting is a bit backwards. Forward rendering looks great with all lights but the only problem is that rendering everything causes an absurd amount of iteration (render time = light count * mesh count). Deferred rendering shows promise (light count + mesh count) but it also means that, in some implementations, you may have to drastically increase the amount of vertices rendered. Additionally, shadows are a bit more difficult to implement. I was thinking of another approach to rendering lights with the speed of deferred rendering but the visual quality of forward rendering.

Basically, there could be two cube maps stored on the GPU which could hold the color, intensity, and position of every light in a scene. The renderer would place every light of the scene into these cube maps in a first pass, then render each mesh in a second pass. The first cube map could add individual RGB and Intensity values of every light, clamped to four individual byte values while the second cube map could hold each light's position (clamped to 3 individual bytes). Next, after each light has been rendered to the cube maps, every mesh of the scene can sample them when they're processed in another pass by the pixel/fragment shader. This means that you get the speed of a deferred renderer (render time = light count + mesh count) with a drastically reduced memory footprint.

 

Would anyone be able to shed some light as to the plausibility of rendering a scene this way? Right now, I have calculated that both buffers would be a total size of about 2.6 Mb, which seems like a hell of a lot less than what is typically required by a deferred renderer. Like I said above, I'm a graphics novice; this is all just theory and I have no idea how it would be implemented in practice, I'm just looking for feedback.

 

My memory calculation is as follows:

4 bytes for the first cube map + 3 bytes for the second cube map = 7 total bytes per pixel, across both cubemaps (math whiz here).

Each cube map is made of 6 2D textures.

Each 2D texture is 256 pixels wide by 256 pixels high.

Therefore, the total memory used by the entire process is 7 bytes * 256 wide * 256 high * 6 textures = 2752512 bytes = 2.6 Mb total.

 

 

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That could only work for non positional lights.

I was initially going to test this with point lights but I guess I'll have to figure out how to add directional and spot lighting. Throwing more textures at the GPU in order to hold each light's properties will end up using as much memory as regular deferred rendering.
At least with point lights, the light vector could be calculated pretty easily (in the fragment shader) by getting the vector from the camera to a mesh and reflecting that against the mesh's surface so that you can find what light[s] to pluck out from the first cube map. Once you do that, then you could also extract the lights position from the second cube map.

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"This means that you get the speed of a deferred renderer (render time = light count + mesh count) with a drastically reduced memory footprint."

 

The speed of a deferred renderer has nothing to do with your algorithm at all. The speed in deferred comes in the fact that you run the pixel shader once for every pixel on the screen. You make pixel shader overdraw = 0. In your algorithm you would still draw an object with a pixel shader and then another object can come along and redraw over that pixel and have to run a pixel shader again (2x for the same pixel).

The algorithm itself doesnt make much sense to me. Why is it a cube map again? What does a mesh use to find the correct light in the cubemap? Why wouldnt it just be a 2D texture of the lights? How exactly does the light get mapped into the cubemap?(its not a 3d Array, its simply 6 faces that designate up down left righ bottom top.

Yes, you don't have the experience enough to finalize your algorithm. I'm planning to do something similar to this, however you have some holes to get to the end and you are in no way related to deferred rendering by this approach.

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The speed of a deferred renderer has nothing to do with your algorithm at all. The speed in deferred comes in the fact that you run the pixel shader once for every pixel on the screen. You make pixel shader overdraw = 0. In your algorithm you would still draw an object with a pixel shader and then another object can come along and redraw over that pixel and have to run a pixel shader again (2x for the same pixel).

 

In this, the pixel shader would be run once for every light to store it in the cube maps, then once more for every mesh when rendering to a final output buffer; just like a deferred renderer. Overdraw can occur regardless of what rendering method is used but it can be reduced if each object is sorted in the scene based on its position from the camera (but I'm not really worried about it at the moment).

 

 

The algorithm itself doesnt make much sense to me. Why is it a cube map again? What does a mesh use to find the correct light in the cubemap? Why wouldnt it just be a 2D texture of the lights? How exactly does the light get mapped into the cubemap?(its not a 3d Array, its simply 6 faces that designate up down left righ bottom top.

 

The lights would be stored in a cubemap for nothing more than indexing really. I imagine it to be a 3D lookup table to get an angle of incidence between the camera, a mesh, and a light in the scene.

 

So for the first pass on the scene, each light's position is stored in one cube map, then its RGB and intensity values in the other. Think of having a skybox but with a bunch of lights' colors and positions only. In order to actually get the data into the cubemaps, I was imagining having the 6 sides of the cube maps set up as render targets that would be bound to the output of a fragment shader.

 

After each light has been rendered to, then in a second fragment shader, a scene's meshes could be rendered to from the view of a camera. Then, as I noted earlier, you could find out how to color each fragment by getting a vector from the camera's position towards the mesh, reflect that vector off the mesh, and finally find which light that reflection vector is pointing at in the cube maps. Since each light's position is stored, you can determine how to color a fragment based on its position and intensity with regards to the final scene.

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Ideas are just that. Consider throwing together a prototype/proof of concept that actually shows the lighting method and relevant shaders, and perhaps allows for some preliminary verification and performance testing. Also consider looking into tiled forward rendering, as I think that's where things are headed in the future.

Edited by Promit

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In this, the pixel shader would be run once for every light to store it in the cube maps

 

Generally, a cubemap represents the scene from a certain view point. For instance, they can be used to render the scene around a point and used to draw rough environment reflections on objects. "rough" because it will only be accurate from one specific position in the scene. Of course it works well for things like a skybox (which is "infinitely" far away and looks the same from every point in the scene).

 

So... what exactly are you putting in your cubemap? Is the end result that there will be a single texel somewhere in the cubemap for each light?

 

 


you could find out how to color each fragment by getting a vector from the camera's position towards the mesh, reflect that vector off the mesh, and finally find which light that reflection vector is pointing at in the cube maps.

 

What are the chances that that reflection vector will line up exactly with the texel that contains the light information? Pretty small. Or does your cubemap contain large areas that cover a light's influence? If so, how would you handle overlapping lights?

 

(also, reflecting the eye vector off the mesh will help you calculate the specular component, what about diffuse?)

 

Maybe I'm just not understanding your description, but I still don't see how your algorithm makes any sense. As Promit suggested, try coming up with a proof of concept. I think it will quickly become obvious where things fall apart.

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I'm not going to go into much depth here, but almost everything you have said really shows your inexperience. Based on that, I would just say don't plan on doing this. You can make games look good with forward rendering, deferred whatever. Don't try to implement the greatest lighting model when you aren't fully grasping things. Really quickly:

"then once more for every mesh when rendering to a final output buffer; just like a deferred renderer."Overdraw can occur regardless of what rendering method is used"
Uh....deferred rendering has 0 pixel shader overdraw. The initial filling of the buffers of course will have some overdraw, but its not like its wasting time running crazy pixel shaders. All lighting shaders are run once for ever pixel. 0 pixel shader (lighting) overdraw.

"but it can be reduced if each object is sorted in the scene based on its position from the camera (but I'm not really worried about it at the moment)."
Yes. In a deferred renderer you would be doing this as well to reduce the G-Buffer initial pass overdraw, but not the lighting pass overdraw.

"Think of having a skybox but with a bunch of lights' colors and positions only."
So I have a 3d light: A and B.  A = vec3(-100,10,0) B = vec3(-110,10,0). Where would these be rendered into the cube map?  If you use simply their position as a vector to render to the cube map....they render to the same spot. A cube map is 6 2D textures, it is not a 3d array. A 3D array would be a cube map with slices cut through it. and even then an actual 3d Texture wouldnt work for your algorithm. Not going to explain to you why because I don't think you will get it.


"Then, as I noted earlier, you could find out how to color each fragment by getting a vector from the camera's position towards the mesh, reflect that vector off the mesh, and"
This wont work. If you are actually rendering the cube map lights as actual spherical geometry... then what you have essentially is cube mapping/environment mapping. But you would have to render all the lights each frame for each mesh. So much wrong with this algorithm.
And if you are talking about rendering geometry, what happens when 2 lights geometry overlap in the cube map?
 

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"What are the chances that that reflection vector will line up exactly with the texel that contains the light information? Pretty small. Or does your cubemap contain large areas that cover a light's influence? If so, how would you handle overlapping lights?"

 

Same thing I said pretty much. If you are only rendering to 1 pixel your light information, then it is still wrong. Noither approaches will work.

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I'd like to also put it on record that shadow mapping with deferred shading is no harder than it is with forward shading, and in fact many games use a very simple deferred approach for shadows (Crysis 1 for example) rather than applying shadows in the forward pass.

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This may only work at all if you sample "cones" rather than reflection vectors, and only for lights at infinity. Surfaces are not perfect mirrors, so one point on the screen that you look at does not correspond to exactly one point in the "sky" (i.e. the cubemap). It corresponds to an area. Unless you come up with something very clever (something like a distance map with a direction vector to the closest "cardinal light" might actually be an idea...) you will need to do a lot of samples so it looks kind of good -- and then it's cheaper to just do normal forward rendering and evaluating all lights as usual.

 

Also, if a light is not "at infinity", let's say 5 meters above you, then an object which is at your position and an object which is  5 meters away will get light from the same angle and with the same intensity. Which is... just wrong, and just looks very bad.

 

Also I'm afraid that you are trying to solve the wrong problem. First of all, forward shading doesn't look better than deferred shading. It will usually look somewhat different, but not necessarily "better" as such. The one big advantage of forward shading is that transparency is a no-brainer (and also antialiasing is easier to get working), but other than that there is no reason why correctly implemented deferred shading should look any worse. On the contrary, you can get a much more consistent lighting and put a lot more shader work into every pixel.

 

On the other hand, deferred shading is not faster.  It is more scaleable in respect of geometry and lights (in particular shadow-casting lights) at the expense of higher memory and bandwidth demands. Deferred shading has a complexity of numbers of lights multiplied with [at most] the resolution plus a more-or-less constant setup, instead of numbers of lights multiplied with number of vertices. Also, deferred shading (if no such thing as clustered DS is done) needs one shadow map at a time, for the one light that is currently being shaded whereas forward shading needs shadow maps for all lights that may affect any of the drawn geometry at once.

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First of all, forward shading doesn't look better than deferred shading. It will usually look somewhat different, but not necessarily "better" as such. The one big advantage of forward shading is that transparency is a no-brainer (and also antialiasing is easier to get working), but other than that there is no reason why correctly implemented deferred shading should look any worse. On the contrary, you can get a much more consistent lighting and put a lot more shader work into every pixel.

 

Most deferred renderers will sacrifice some precision with normals, position(depth reconstruction is not 100% accurate) and with other paramaters that can cause some quality loss on final image. Luckily this is mostly last gen games where this is visible.

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This technique would work for the one point in the scene that you render as the center of the cube maps.  When you render the lights into the cube map, you're doing it relative to this one point.  So that one point would be lit correctly.  Everything else would be skewed.

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I used a technique on the Wii that's very similar to the one mentioned in the OP, to get lots of dynamic lights on it's crappy hardware... except, instead of global cube-maps for the scene, each object had it's own cube-map, so that directionality and attenuation worked properly (at least on a per-mesh granularity - not very good for large meshes). Also, instead of cube-maps, we used sphere-maps for simplicity.... and you can't just render a light into a single texel, you have to render a large diffused blob of light.

The lighting is obviously much more approximate than doing it traditionally per-pixel -- the surface normal is evaluated per-pixel, but the attenuation and direction to light are evaluated per mesh. This means that for small meshes, it's pretty good, but for large meshes, all lights start to look like directional lights.

The other down-side is that you can't use nice BRDF's like Blinn-Phong or anything...

 

In general, this is part of a family of techniques known as image based lighting, and yes, it's common to combine a bunch of non-primary lights into a cube-map, etc -- e.g. think of every pixel in your sky-dome as a small directional light. Using it as a replacement for primary lights, across an entire scene, is a bit less popular.

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I used a technique on the Wii that's very similar to the one mentioned in the OP, to get lots of dynamic lights on it's crappy hardware... except, instead of global cube-maps for the scene, each object had it's own cube-map, so that directionality and attenuation worked properly (at least on a per-mesh granularity - not very good for large meshes). Also, instead of cube-maps, we used sphere-maps for simplicity.... and you can't just render a light into a single texel, you have to render a large diffused blob of light.

The lighting is obviously much more approximate than doing it traditionally per-pixel -- the surface normal is evaluated per-pixel, but the attenuation and direction to light are evaluated per mesh. This means that for small meshes, it's pretty good, but for large meshes, all lights start to look like directional lights.

The other down-side is that you can't use nice BRDF's like Blinn-Phong or anything...

 

In general, this is part of a family of techniques known as image based lighting, and yes, it's common to combine a bunch of non-primary lights into a cube-map, etc -- e.g. think of every pixel in your sky-dome as a small directional light. Using it as a replacement for primary lights, across an entire scene, is a bit less popular.

For kinghunt 

 

I did very similar trick but instead of sphere maps I used spherical harmonics. I also calculated aproximated visibility function per object against all other objects. This was so fast that even particles could be light emitters.

Edited by kalle_h

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While I can see how image-based lighting might work great on mobile devices, how do these translate to desktops where the ALU/TEX ratio is much higher? I would guess that using literally abundant ALU to compute a dozen lights that are visible from one fragment may very well be faster than to do yet an additional texture lookup?

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While I can see how image-based lighting might work great on mobile devices, how do these translate to desktops where the ALU/TEX ratio is much higher? I would guess that using literally abundant ALU to compute a dozen lights that are visible from one fragment may very well be faster than to do yet an additional texture lookup?

In console/PC games, it's standard to use IBL for background/fill/bounce/ambient lights (GI), instead of a flat ambient colour, and then compute the direct lighting analytically.

 

For film-quality IBL, you don't pre-convolve the probes, and each pixel has to read thousands of importance-sampled values from the IBL probes and integrate them using the BRDF (which is both ALU and TEX heavy)...

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While I can see how image-based lighting might work great on mobile devices, how do these translate to desktops where the ALU/TEX ratio is much higher? I would guess that using literally abundant ALU to compute a dozen lights that are visible from one fragment may very well be faster than to do yet an additional texture lookup?

In console/PC games, it's standard to use IBL for background/fill/bounce/ambient lights (GI), instead of a flat ambient colour, and then compute the direct lighting analytically.

 

For film-quality IBL, you don't pre-convolve the probes, and each pixel has to read thousands of importance-sampled values from the IBL probes and integrate them using the BRDF (which is both ALU and TEX heavy)...

 

 

Which is why most people pre-convolve the probes. I'm not sure UE4 does, then again I'm not sure exactly what it is they're even doing. All I've gathered is "cube map array" and their ability to relight the probes in realtime.

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While I can see how image-based lighting might work great on mobile devices, how do these translate to desktops where the ALU/TEX ratio is much higher? I would guess that using literally abundant ALU to compute a dozen lights that are visible from one fragment may very well be faster than to do yet an additional texture lookup?

In console/PC games, it's standard to use IBL for background/fill/bounce/ambient lights (GI), instead of a flat ambient colour, and then compute the direct lighting analytically.

 

For film-quality IBL, you don't pre-convolve the probes, and each pixel has to read thousands of importance-sampled values from the IBL probes and integrate them using the BRDF (which is both ALU and TEX heavy)...

 

 

Which is why most people pre-convolve the probes. I'm not sure UE4 does, then again I'm not sure exactly what it is they're even doing. All I've gathered is "cube map array" and their ability to relight the probes in realtime.

 

 

They pre-convolve their specular probes, by convolving the specular BRDF with a given roughness assuming that V=N. They also take the standard approach of storing the results for different roughness values in the mip levels of the cubemap (higher roughnesses go into lower-res mip levels), and then selecting the mip per-pixel based on the surface roughness. They also refactored things a bit so that they can approximate the appropriate BRDF response for different viewing angles by precomputing values into lookup textures and indexing them at runtime. This sort of approach is becoming fairly common.

I'm not sure what they do for diffuse, but I would assume that they store SH probes which is what most people do these days. 

Edited by MJP

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      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
    • By TheChubu
      The Khronos™ Group, an open consortium of leading hardware and software companies, announces from the SIGGRAPH 2017 Conference the immediate public availability of the OpenGL® 4.6 specification. OpenGL 4.6 integrates the functionality of numerous ARB and EXT extensions created by Khronos members AMD, Intel, and NVIDIA into core, including the capability to ingest SPIR-V™ shaders.
      SPIR-V is a Khronos-defined standard intermediate language for parallel compute and graphics, which enables content creators to simplify their shader authoring and management pipelines while providing significant source shading language flexibility. OpenGL 4.6 adds support for ingesting SPIR-V shaders to the core specification, guaranteeing that SPIR-V shaders will be widely supported by OpenGL implementations.
      OpenGL 4.6 adds the functionality of these ARB extensions to OpenGL’s core specification:
      GL_ARB_gl_spirv and GL_ARB_spirv_extensions to standardize SPIR-V support for OpenGL GL_ARB_indirect_parameters and GL_ARB_shader_draw_parameters for reducing the CPU overhead associated with rendering batches of geometry GL_ARB_pipeline_statistics_query and GL_ARB_transform_feedback_overflow_querystandardize OpenGL support for features available in Direct3D GL_ARB_texture_filter_anisotropic (based on GL_EXT_texture_filter_anisotropic) brings previously IP encumbered functionality into OpenGL to improve the visual quality of textured scenes GL_ARB_polygon_offset_clamp (based on GL_EXT_polygon_offset_clamp) suppresses a common visual artifact known as a “light leak” associated with rendering shadows GL_ARB_shader_atomic_counter_ops and GL_ARB_shader_group_vote add shader intrinsics supported by all desktop vendors to improve functionality and performance GL_KHR_no_error reduces driver overhead by allowing the application to indicate that it expects error-free operation so errors need not be generated In addition to the above features being added to OpenGL 4.6, the following are being released as extensions:
      GL_KHR_parallel_shader_compile allows applications to launch multiple shader compile threads to improve shader compile throughput WGL_ARB_create_context_no_error and GXL_ARB_create_context_no_error allow no error contexts to be created with WGL or GLX that support the GL_KHR_no_error extension “I’m proud to announce OpenGL 4.6 as the most feature-rich version of OpenGL yet. We've brought together the most popular, widely-supported extensions into a new core specification to give OpenGL developers and end users an improved baseline feature set. This includes resolving previous intellectual property roadblocks to bringing anisotropic texture filtering and polygon offset clamping into the core specification to enable widespread implementation and usage,” said Piers Daniell, chair of the OpenGL Working Group at Khronos. “The OpenGL working group will continue to respond to market needs and work with GPU vendors to ensure OpenGL remains a viable and evolving graphics API for all its customers and users across many vital industries.“
      The OpenGL 4.6 specification can be found at https://khronos.org/registry/OpenGL/index_gl.php. The GLSL to SPIR-V compiler glslang has been updated with GLSL 4.60 support, and can be found at https://github.com/KhronosGroup/glslang.
      Sophisticated graphics applications will also benefit from a set of newly released extensions for both OpenGL and OpenGL ES to enable interoperability with Vulkan and Direct3D. These extensions are named:
      GL_EXT_memory_object GL_EXT_memory_object_fd GL_EXT_memory_object_win32 GL_EXT_semaphore GL_EXT_semaphore_fd GL_EXT_semaphore_win32 GL_EXT_win32_keyed_mutex They can be found at: https://khronos.org/registry/OpenGL/index_gl.php
      Industry Support for OpenGL 4.6
      “With OpenGL 4.6 our customers have an improved set of core features available on our full range of OpenGL 4.x capable GPUs. These features provide improved rendering quality, performance and functionality. As the graphics industry’s most popular API, we fully support OpenGL and will continue to work closely with the Khronos Group on the development of new OpenGL specifications and extensions for our customers. NVIDIA has released beta OpenGL 4.6 drivers today at https://developer.nvidia.com/opengl-driver so developers can use these new features right away,” said Bob Pette, vice president, Professional Graphics at NVIDIA.
      "OpenGL 4.6 will be the first OpenGL release where conformant open source implementations based on the Mesa project will be deliverable in a reasonable timeframe after release. The open sourcing of the OpenGL conformance test suite and ongoing work between Khronos and X.org will also allow for non-vendor led open source implementations to achieve conformance in the near future," said David Airlie, senior principal engineer at Red Hat, and developer on Mesa/X.org projects.

      View full story
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