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• By elect
Hi,
ok, so, we are having problems with our current mirror reflection implementation.
At the moment we are doing it very simple, so for the i-th frame, we calculate the reflection vectors given the viewPoint and some predefined points on the mirror surface (position and normal).
Then, using the least squared algorithm, we find the point that has the minimum distance from all these reflections vectors. This is going to be our virtual viewPoint (with the right orientation).
After that, we render offscreen to a texture by setting the OpenGL camera on the virtual viewPoint.
And finally we use the rendered texture on the mirror surface.
So far this has always been fine, but now we are having some more strong constraints on accuracy.
What are our best options given that:
- we have a dynamic scene, the mirror and parts of the scene can change continuously from frame to frame
- we have about 3k points (with normals) per mirror, calculated offline using some cad program (such as Catia)
- all the mirror are always perfectly spherical (with different radius vertically and horizontally) and they are always convex
- a scene can have up to 10 mirror
- it should be fast enough also for vr (Htc Vive) on fastest gpus (only desktops)

Looking around, some papers talk about calculating some caustic surface derivation offline, but I don't know if this suits my case
Also, another paper, used some acceleration structures to detect the intersection between the reflection vectors and the scene, and then adjust the corresponding texture coordinate. This looks the most accurate but also very heavy from a computational point of view.

Other than that, I couldn't find anything updated/exhaustive around, can you help me?

• Hello all,
I am currently working on a game engine for use with my game development that I would like to be as flexible as possible.  As such the exact requirements for how things should work can't be nailed down to a specific implementation and I am looking for, at least now, a default good average case scenario design.
Here is what I have implemented:
Deferred rendering using OpenGL Arbitrary number of lights and shadow mapping Each rendered object, as defined by a set of geometry, textures, animation data, and a model matrix is rendered with its own draw call Skeletal animations implemented on the GPU.   Model matrix transformation implemented on the GPU Frustum and octree culling for optimization Here are my questions and concerns:
Doing the skeletal animation on the GPU, currently, requires doing the skinning for each object multiple times per frame: once for the initial geometry rendering and once for the shadow map rendering for each light for which it is not culled.  This seems very inefficient.  Is there a way to do skeletal animation on the GPU only once across these render calls? Without doing the model matrix transformation on the CPU, I fail to see how I can easily batch objects with the same textures and shaders in a single draw call without passing a ton of matrix data to the GPU (an array of model matrices then an index for each vertex into that array for transformation purposes?) If I do the matrix transformations on the CPU, It seems I can't really do the skinning on the GPU as the pre-transformed vertexes will wreck havoc with the calculations, so this seems not viable unless I am missing something Overall it seems like simplest solution is to just do all of the vertex manipulation on the CPU and pass the pre-transformed data to the GPU, using vertex shaders that do basically nothing.  This doesn't seem the most efficient use of the graphics hardware, but could potentially reduce the number of draw calls needed.

Really, I am looking for some advice on how to proceed with this, how something like this is typically handled.  Are the multiple draw calls and skinning calculations not a huge deal?  I would LIKE to save as much of the CPU's time per frame so it can be tasked with other things, as to keep CPU resources open to the implementation of the engine.  However, that becomes a moot point if the GPU becomes a bottleneck.

• Hello!
I would like to introduce Diligent Engine, a project that I've been recently working on. Diligent Engine is a light-weight cross-platform abstraction layer between the application and the platform-specific graphics API. Its main goal is to take advantages of the next-generation APIs such as Direct3D12 and Vulkan, but at the same time provide support for older platforms via Direct3D11, OpenGL and OpenGLES. Diligent Engine exposes common front-end for all supported platforms and provides interoperability with underlying native API. Shader source code converter allows shaders authored in HLSL to be translated to GLSL and used on all platforms. Diligent Engine supports integration with Unity and is designed to be used as a graphics subsystem in a standalone game engine, Unity native plugin or any other 3D application. It is distributed under Apache 2.0 license and is free to use. Full source code is available for download on GitHub.
Features:
True cross-platform Exact same client code for all supported platforms and rendering backends No #if defined(_WIN32) ... #elif defined(LINUX) ... #elif defined(ANDROID) ... No #if defined(D3D11) ... #elif defined(D3D12) ... #elif defined(OPENGL) ... Exact same HLSL shaders run on all platforms and all backends Modular design Components are clearly separated logically and physically and can be used as needed Only take what you need for your project (do not want to keep samples and tutorials in your codebase? Simply remove Samples submodule. Only need core functionality? Use only Core submodule) No 15000 lines-of-code files Clear object-based interface No global states Key graphics features: Automatic shader resource binding designed to leverage the next-generation rendering APIs Multithreaded command buffer generation 50,000 draw calls at 300 fps with D3D12 backend Descriptor, memory and resource state management Modern c++ features to make code fast and reliable The following platforms and low-level APIs are currently supported:
Windows Desktop: Direct3D11, Direct3D12, OpenGL Universal Windows: Direct3D11, Direct3D12 Linux: OpenGL Android: OpenGLES MacOS: OpenGL iOS: OpenGLES API Basics
Initialization
The engine can perform initialization of the API or attach to already existing D3D11/D3D12 device or OpenGL/GLES context. For instance, the following code shows how the engine can be initialized in D3D12 mode:
#include "RenderDeviceFactoryD3D12.h" using namespace Diligent; // ...  GetEngineFactoryD3D12Type GetEngineFactoryD3D12 = nullptr; // Load the dll and import GetEngineFactoryD3D12() function LoadGraphicsEngineD3D12(GetEngineFactoryD3D12); auto *pFactoryD3D11 = GetEngineFactoryD3D12(); EngineD3D12Attribs EngD3D12Attribs; EngD3D12Attribs.CPUDescriptorHeapAllocationSize[0] = 1024; EngD3D12Attribs.CPUDescriptorHeapAllocationSize[1] = 32; EngD3D12Attribs.CPUDescriptorHeapAllocationSize[2] = 16; EngD3D12Attribs.CPUDescriptorHeapAllocationSize[3] = 16; EngD3D12Attribs.NumCommandsToFlushCmdList = 64; RefCntAutoPtr<IRenderDevice> pRenderDevice; RefCntAutoPtr<IDeviceContext> pImmediateContext; SwapChainDesc SwapChainDesc; RefCntAutoPtr<ISwapChain> pSwapChain; pFactoryD3D11->CreateDeviceAndContextsD3D12( EngD3D12Attribs, &pRenderDevice, &pImmediateContext, 0 ); pFactoryD3D11->CreateSwapChainD3D12( pRenderDevice, pImmediateContext, SwapChainDesc, hWnd, &pSwapChain ); Creating Resources
Device resources are created by the render device. The two main resource types are buffers, which represent linear memory, and textures, which use memory layouts optimized for fast filtering. To create a buffer, you need to populate BufferDesc structure and call IRenderDevice::CreateBuffer(). The following code creates a uniform (constant) buffer:
BufferDesc BuffDesc; BufferDesc.Name = "Uniform buffer"; BuffDesc.BindFlags = BIND_UNIFORM_BUFFER; BuffDesc.Usage = USAGE_DYNAMIC; BuffDesc.uiSizeInBytes = sizeof(ShaderConstants); BuffDesc.CPUAccessFlags = CPU_ACCESS_WRITE; m_pDevice->CreateBuffer( BuffDesc, BufferData(), &m_pConstantBuffer ); Similar, to create a texture, populate TextureDesc structure and call IRenderDevice::CreateTexture() as in the following example:
TextureDesc TexDesc; TexDesc.Name = "My texture 2D"; TexDesc.Type = TEXTURE_TYPE_2D; TexDesc.Width = 1024; TexDesc.Height = 1024; TexDesc.Format = TEX_FORMAT_RGBA8_UNORM; TexDesc.Usage = USAGE_DEFAULT; TexDesc.BindFlags = BIND_SHADER_RESOURCE | BIND_RENDER_TARGET | BIND_UNORDERED_ACCESS; TexDesc.Name = "Sample 2D Texture"; m_pRenderDevice->CreateTexture( TexDesc, TextureData(), &m_pTestTex ); Initializing Pipeline State
Diligent Engine follows Direct3D12 style 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.)
To create a shader, populate ShaderCreationAttribs structure. An important member is ShaderCreationAttribs::SourceLanguage. The following are valid values for this member:
SHADER_SOURCE_LANGUAGE_DEFAULT  - The shader source format matches the underlying graphics API: HLSL for D3D11 or D3D12 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. See shader converter for details. SHADER_SOURCE_LANGUAGE_GLSL  - The shader source is in GLSL. There is currently no GLSL to HLSL converter. To allow grouping of resources based on the frequency of expected change, Diligent Engine introduces classification of shader variables:
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. This post describes the resource binding model in Diligent Engine.
The following is an example of shader initialization:
To create a pipeline state object, define instance of PipelineStateDesc structure. The structure defines the pipeline specifics such as if the pipeline is a compute pipeline, number and format of render targets as well as depth-stencil format:
// This is a graphics pipeline PSODesc.IsComputePipeline = false; PSODesc.GraphicsPipeline.NumRenderTargets = 1; PSODesc.GraphicsPipeline.RTVFormats[0] = TEX_FORMAT_RGBA8_UNORM_SRGB; PSODesc.GraphicsPipeline.DSVFormat = TEX_FORMAT_D32_FLOAT; The structure also defines depth-stencil, rasterizer, blend state, input layout and other parameters. For instance, rasterizer state can be defined as in the code snippet below:
// Init rasterizer state RasterizerStateDesc &RasterizerDesc = PSODesc.GraphicsPipeline.RasterizerDesc; RasterizerDesc.FillMode = FILL_MODE_SOLID; RasterizerDesc.CullMode = CULL_MODE_NONE; RasterizerDesc.FrontCounterClockwise = True; RasterizerDesc.ScissorEnable = True; //RSDesc.MultisampleEnable = false; // do not allow msaa (fonts would be degraded) RasterizerDesc.AntialiasedLineEnable = False; When all fields are populated, call IRenderDevice::CreatePipelineState() to create the PSO:
Shader resource binding in Diligent Engine is based on grouping variables in 3 different groups (static, mutable and dynamic). Static variables 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. They are bound directly to the shader object:

m_pPSO->CreateShaderResourceBinding(&m_pSRB); Dynamic and mutable resources are then bound through SRB object:
m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "tex2DDiffuse")->Set(pDiffuseTexSRV); m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "cbRandomAttribs")->Set(pRandomAttrsCB); The difference between mutable and dynamic resources is that mutable ones can only be set once for every instance of a shader resource binding. Dynamic resources can be set multiple times. It is important to properly set the variable type as this may affect performance. Static variables are generally most efficient, followed by mutable. Dynamic variables are most expensive from performance point of view. This post explains shader resource binding in more details.
Setting the Pipeline State and Invoking Draw Command
Before any draw command can be invoked, all required vertex and index buffers as well as the pipeline state should be bound to the device context:
// Clear render target const float zero[4] = {0, 0, 0, 0}; m_pContext->ClearRenderTarget(nullptr, zero); // 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); m_pContext->SetPipelineState(m_pPSO); Also, all shader resources must be committed to the device context:
m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES); When all required states and resources are bound, IDeviceContext::Draw() can be used to execute draw command or IDeviceContext::DispatchCompute() can be used to execute compute command. Note that for a draw command, graphics pipeline must be bound, and for dispatch command, compute pipeline must be bound. Draw() 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); Tutorials and Samples
The GitHub repository contains a number of tutorials and sample applications that demonstrate the API usage.

AntTweakBar sample demonstrates how to use AntTweakBar library to create simple user interface.

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 textures, using compute shaders and unordered access views, etc.

The repository includes Asteroids performance benchmark based on this demo developed by Intel. It renders 50,000 unique textured asteroids and lets compare performance of D3D11 and D3D12 implementations. Every asteroid is a combination of one of 1000 unique meshes and one of 10 unique textures.

Integration with Unity
Diligent Engine supports integration with Unity through Unity low-level native plugin interface. The engine relies on Native API Interoperability to attach to the graphics API initialized by Unity. After Diligent Engine device and context are created, they can be used us usual to create resources and issue rendering commands. GhostCubePlugin shows an example how Diligent Engine can be used to render a ghost cube only visible as a reflection in a mirror.

• By Yxjmir
I'm trying to load data from a .gltf file into a struct to use to load a .bin file. I don't think there is a problem with how the vertex positions are loaded, but with the indices. This is what I get when drawing with glDrawArrays(GL_LINES, ...):

Also, using glDrawElements gives a similar result. Since it looks like its drawing triangles using the wrong vertices for each face, I'm assuming it needs an index buffer/element buffer. (I'm not sure why there is a line going through part of it, it doesn't look like it belongs to a side, re-exported it without texture coordinates checked, and its not there)
I'm using jsoncpp to load the GLTF file, its format is based on JSON. Here is the gltf struct I'm using, and how I parse the file:
glBindVertexArray(g_pGame->m_VAO);
glDrawElements(GL_LINES, g_pGame->m_indices.size(), GL_UNSIGNED_BYTE, (void*)0); // Only shows with GL_UNSIGNED_BYTE
glDrawArrays(GL_LINES, 0, g_pGame->m_vertexCount);
So, I'm asking what type should I use for the indices? it doesn't seem to be unsigned short, which is what I selected with the Khronos Group Exporter for blender. Also, am I reading part or all of the .bin file wrong?
Test.gltf
Test.bin

• That means how do I use base DirectX or OpenGL api's to make a physics based destruction simulation?
Will it be just smart rendering or something else is required?

# OpenGL Texture compression DDS / S3TC

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Hey,

About texture compression... Never used it so far, but I just made an (OpenGL) program that loads a DDS file. So far so good, but before really implementing it in my engine, I need some good reasons. Well, what I can think of:
- No time wasted generating mip-maps
- Smaller disk size
- Extra features such as cubeMap / 3D textures
- Allows to use bigger resolutions

Then on the other hand...
- Lower quality
- Slower rendering?? Or is it actually faster (less bandwidth)??

The lower quality probably depends on the compression settings I guess, and images that really need detail still can use uncompressed formats. But, how bad is the loss really? I can't really see a difference usually. But I didn't have a lot of examples.

About the performance. I've been tought, 100 years ago, that decompressing takes time. Not sure how the video-card does things, but does the decompression hit the performance? The only thing I read is that is can actually boost the performance because less bandwidth is used. In my case I have quite a lot surface textures (512 x 512, 1024 x 1024, resolutions like that).

A last question. How to calculate the video memory usage of a compressed texture? Is it equal to the amount of bytes pixeldata you read? Or does OpenGL / GPU convert the data?

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Lower quality[/quote]

Not necessarily, while using same space as standard texture, S3TC (DXT1) compressed one can have 8-times the size of uncompressed one actually, while still keeping very good quality - so you can actually have a lot more micro details on texture, even with a little less colors (still not too much visible difference between s3tc compressed one and uncompressed - in most cases...)

Slower rendering?? Or is it actually faster (less bandwidth)??[/quote]

Actually it is faster, less bandwidth, and also u have less memory storage.

About the performance. I've been tought, 100 years ago, that decompressing takes time. Not sure how the video-card does things, but does the decompression hit the performance?[/quote]

Actually S3TC compressions are hardware implemented on GPU, so it won't take any time more than using standard uncompressed texture.

How to calculate the video memory usage of a compressed texture?[/quote]

Memory usage = Number of pixels * Bits per pixel / Compression Ratio

Or does OpenGL / GPU convert the data?[/quote]

The good thing on S3TC compressions is that GPU still keeps them compressed in VRAM - e.g. they're actually a lot smaller than standard textures.

Note that S3TC compressions are a must for Megatextures.

Btw. I think I'm still having some S3TC compression code lying around if you would like to try encoding, but still I don't know if its patented and for how long (I wrote it just out of curiosity and I even read patent, my code is different than what they describe )

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In general compression is going to be a win. It can significantly ease the burden on your memory usage, and it helps with bandwidth as well. The GPU can decode them on the fly (since S3TC is designed to be very simple to decode a 4x4 block) so you don't need to worry about any added cost for the decode. You do have to be careful though with quality, for certain cases it's very easy to end up with a really crappy-looking texture once you've compressed them.

Here are some general tips. I'm going to use the D3D10/D3D11 terminology for the different compression formats, since I don't know the corresponding OpenGL names (sorry!):

1. Use a good compressor! This is key. Some are much better than others. For offline compression, I recommend using the ATI_Compress library. It's dead simple, it's multithreaded, and has great quality. We used to Nvidia texture tools at work since it's open source, but the quality was worse and it was significantly slower.

2. Have the option to opt out of compression for certain textures. You're bound to find a few cases where the hit in quality just isn't worth it...for instance anything with a really smooth gradient usually ends up being paletized pretty badly.

3. Use the right format! BC1 has the lowest memory footprint for an RGB texture, but also doesn't have an alpha channel. BC2 and BC3 do have alpha channels, with different means of encoding them (most people just stick to BC3). For monochrome textures, you'll want BC4. It has 1 hi-quality channel (basically the alpha channel from BC3). For normal maps, you'll want to use BC5 which has 2 hi-quality channels (store XY and reconstruct Z in the shader). If BC4 and BC5 aren't available on your target spec, then you can use BC3 for normal maps and put the X in the alpha channel and Y in the green channel and then reconstruct Z in the shader (those are the two channels with the most precision).

4. For color maps you can get a bit better quality by determining the min and max values in the texture, and then rescaling that range to [0, 1]. Then in the shader you use the min and max to scale it back to the normal.

5. BC6 and BC7 are really awesome (HDR, and hi-quality LDR respectively), but only available on DX11-class hardware. There's also not really any tools support for it yet. The D3DX library can encode to it, but it's super slow. There's also a sample in the SDK that does the encoding on the GPU using a compute shader, but it's pretty bare bones and doesn't support cube maps or mipmaps.

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Hey Vilem! It's been a while. Sorry for forgetting to mail you a year ago. It suddenly got so busy with people offering help on T22

Thanks for the info MJP & Vilem. These arguments are good enough to put DDS support in the engine. I thought decoding would give a small hit, but having the hardware doing it for "free" is awesome.

Images with compressing quality issues can still keep using uncompressed formats. About that... asides from smooth gradients are there particular cases that have quality problems?
- Textures using the alpha channel for transparency (foliages, metal fences, ...)
- NormalMaps with small details
- Images with a lot of small details, but not varying colors (a sand texture for example)
Most of the images we're using are indoor material textures such as a concrete wall or wood floor btw.

Not sure where BC1..7 stands for. While coding a bit I came across DXT1, DXT3 and DXT5. Are those the same?

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Sorry for forgetting to mail you a year ago. It suddenly got so busy with people offering help on T22[/quote]

No problem, I watch your T22 blog from time to time and your project looks very very promising!

Not sure where BC1..7 stands for. While coding a bit I came across DXT1, DXT3 and DXT5. Are those the same?[/quote]

AFAIR BC* is naming system of Direct3D, while DXT* are names used in OpenGL:

DXT1 is actually BC1
DXT3 is actually BC3
DXT5 is actually BC5

Actually I think there are also DXT2 and DXT4 (but these aren't used commonly and I'm also not sure if GL implements them), BC6 and BC7 are new things, I think that BPTC is whats standing in OpenGL instead of BC7 in Direct3D.

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Yeah DX9 used to call them DXT* and the old OpenGL extensions also called them DXT, but in DX10 onwards they started calling them BC* (where BC stands for "block compression"). I have no idea if the names have changed with the newer (3.x - 4.x) version of OpenGL, which is why I just used the DX10 names. For quick reference:

BC1 - 5:6:5 RGB + 1bit alpha. DXT1 in DX9/GL extensions. 1:6 compression ratio
BC2 - 5:6:5 RGB + 4bit explicit alpha (better for non-coherent alpha values). DXT3 in DX9/GL extensions. 1:4 compression
BC3 - 5:6:5 RGB + 8bit interpreted alpha (better for coherent alpha values). DXT5 in DX9/GL extensions. 1:4 compression
BC4 - 8bit interpreted R, similar to the alpha from BC3. Was previously known as ATI1N in DX9, I think it was called LATC1 in GL extensions. 1:2 compression
BC5 - 8bit interpreted RG, basically just double BC4 channels. Was previously known as ATI2N in DX9, LATC2 in GL extensions. Referred to as "3Dc" in ATI marketing. 1:2 compression
BC6H - 16:16:16 floating point RGB. No idea what this is called in OpenGL.1:6 compression ratio
BC7 - 4-7bit RGB + 0-8bit alpha. Actually a combination of different encoding modes, where the best mode is chosen for each 4x4 block to best represent the data. 1:4 compression ratio

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BC4 = RED_RGTC1 in OpenGL
BC5 = RG_RGTC2 in OpenGL
from http://www.opengl.org/registry/specs/ARB/texture_compression_rgtc.txt (in Core from 3.0)

BC6H = BPTC_UNORM / SRGB_ALPHA_BPTC_UNORM
BC7 = BPTC_SIGNED_FLOAT / BPTC_UNSIGNED_FLOAT
from http://www.opengl.org/registry/specs/ARB/texture_compression_bptc.txt (in Core from 4.2)

Both extensions especially mentions compatibility with DirectX.

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BC6H = BPTC_UNORM / SRGB_ALPHA_BPTC_UNORM
BC7 = BPTC_SIGNED_FLOAT / BPTC_UNSIGNED_FLOAT
from http://www.opengl.or...ession_bptc.txt (in Core from 4.2)

I think these are backwards

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Right! I'm locked and loaded now, time to implement it, and start the compressor! Thank you all

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[quote name='Martins Mozeiko' timestamp='1316122987' post='4862230']
BC6H = BPTC_UNORM / SRGB_ALPHA_BPTC_UNORM
BC7 = BPTC_SIGNED_FLOAT / BPTC_UNSIGNED_FLOAT
from http://www.opengl.or...ession_bptc.txt (in Core from 4.2)

I think these are backwards
[/quote]
Oops! Yes, you are right. BC7 = BPTC_xyz_FLOAT, BC6H = xyz_BPTC_UNORM.