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Posts Tagged ‘OpenGL’

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The tutorial The Art of Texturing Using the OpenGL Shading Language has been included in OpenGL.org website in OpenGL API OpenGL Shading Language Sample Code & Tutorials section. Rather cool…

As I said in this news, the release of Catalyst 8.10 BETA comes with a nice bugfix: vertex texture fetching is now operational on Radeon (at least on my Radeon HD 4850). From 2 or 3 months, Catalyst makes it possible to fetch texture from inside a vertex shader. You can see with GPU Caps Viewer how many texture units are exposed in a vertex shader for your Radeon:

But so far, vertex texture fetching in GLSL didn’t work due to a bug in the driver. But now this is an old story, since VTF works well. For more details about vertex displacement mapping, you can read this rather old (2 years!) tutorial: Vertex Displacement Mapping using GLSL.

This very cool news makes me want to create a new benchmark based on VTF!

I’ve only tested the XP version of Catalyst 8.10. If someone has tested the Vista version, feel free to post a comment…

Next step for ATI driver team: enable geometry texture fetching: allows texture fetching inside a geometry shader…

See you soon!

A user from oZone3D.Net forum asked me some info about the GLSL support of Intel graphics chips. It’s wellknown (sorry Intel) that Intel has a bad OpenGL support in its Windows drivers and even if Intel’s graphics drivers support OpenGL 1.5, there is still a lack of GLSL support. We can’t find the GL_ARB_shading_language_100 extension (this extension means the graphics driver supports the OpenGL shading language) and this extension should be supported by any OpenGL 1.5 compliant graphics driver. You can use GPU Caps Viewer to check for the avaibility of GL_ARB_shading_language_100 (in OpenGL Caps tab).

Here is an example of a Intel’s graphics driver that support openGL 1.5 without supporting GLSL:
- Mobile IntelR 965 Express Chipset Family

For more examples, look at users’s submissions here: www.ozone3d.net/gpu/db/

Okay this is my analysis, but what is the Intel point of view? Here is the answer:
- x3100 & OpenGL Shader (GLSL) thread
- Intel’s answer

I think GLSL support with Windows is not a priority for Intel…

Here is the list of OpenGL extensions supported by Forceware 174.20 drivers.

OpenGL Extensions: 161 extensions

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Here is the list of OpenGL extensions supported by Catalyst 8.3 drivers. There are 96 extensions.

• Drivers Version: 8.471.0.0 – Catalyst 08.3
• ATI Catalyst Version String: 08.3
• ATI Catalyst Release Version String: 8.471-080225a1-059746C-ATI

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This demo uses instancing techniques (simple instancing, pseudo-instancing and geometry instancing(or GI)) to render a ring made of 10,000 small spheres. The demo is delivered in 5 versions:

• each sphere is made of 1,800 triangles (18 millions triangles for the whole ring)
• each sphere is made of 800 triangles (8 millions triangles for the whole ring)
• each sphere is made of 200 triangles (2 millions triangles for the whole ring)
• each sphere is made of 72 triangles (720,000 triangles for the whole ring)
• each sphere is made of 18 triangles (180,000 triangles for the whole ring)

I added in the last moment a bonus: a 20,000 instances version, each instance made of 5,000 triangles. We get the monstruous count of 100 millions triangles (file Demo_Instancing_100MTriangles_20kInstances.exe).

DOWNLOAD

OpenGL Instancing DemoPack – (2676k)

Several instancing techniques are used and you can select them with F1 to F6 keys.

• F1: simple instancing with camera frustum culling: there is one source for geometry (a mesh) and it’s rendered for each instance. The tranformation matrix calculation is done on the CPU as well as the camera frustum test. OpenGL rendering uses the glDrawElements() function.
• F2: simple instancing without camera frustum culling: there is one source for geometry (a mesh) and it’s rendered for each instance. The tranformation matrix calculation is done on the CPU but there is no longer camera frustum test. OpenGL rendering uses the glDrawElements() function.
• F3: slow pseudo-instancing: there is one source for geometry (a mesh) and it’s rendered for each instance. Now the tranformation matrix calculation is done on the GPU and per-instance data are passed via uniform variables. There is no camera frustum test. OpenGL rendering uses the glDrawElements() function.
• F4: pseudo-instancing: there is one source for geometry (a mesh) and it’s rendered for each instance. The tranformation matrix calculation is done on the GPU and per-instance data are passed via persistent vertex attributes (like texture coordinates or color). This technique has been shown by NVIDIA in the following whitepaper: GLSL Pseudo-Instancing. There is no camera frustum test. OpenGL rendering uses the glDrawElements() function.
• F5: geometry instancing: it’s the real hardware instancing. There is one source for geometry (a mesh) and rendering is done by batchs of 400 instances per draw-call. The whole rendering of the ring requires 25 draw-calls instead of 10,000. The tranformation matrix calculation is done on the GPU and per-batch data is passed via uniform arrays. There is no camera frustum test. OpenGL rendering uses the glDrawElementsInstancedEXT() function. Currently, only NVIDIA GeForce 8 (and higher) support this function.
• F6: geometry instancing with persistant vertex attributes: it’s the hardware instancing coupled with the transmission of parameters is done via the persistent vertex attributes. But the number of persistent vertex attributes is very limited. The best I did is to render 4 instances per draw-call. But oddly, I got the best results with 2 instances per draw-call. In that case, the rendering of whole ring requires 5000 draw-calls. The tranformation matrix calculation is done on the GPU and per-batch data is passed via uniform arrays. There is no camera frustum test. OpenGL rendering uses the glDrawElementsInstancedEXT() function. Currently, only NVIDIA GeForce 8 (and higher) support this function.

Ok now, let’s see some results with a NVIDIA GeForce 8800 GTX and an ATI Radeon HD 3870. Both cards have been tested with an AMD 64 3800+.

18 millions triangles – 1800 tri/instance

NVIDIA GeForce 8800 GTX – Forceware 169.38 XP32

• F1: 223MTris/sec – 13FPS
• F2: 223MTris/sec – 13FPS
• F3: 223MTris/sec – 13FPS
• F4: 223MTris/sec – 13FPS
• F5: 223MTris/sec – 13FPS
• F6: 171MTris/sec – 10FPS

ATI Radeon HD 3870 – Catalyst 8.2 XP32

• F1: 429MTris/sec – 25FPS
• F2: 463MTris/sec – 27FPS
• F3: 446MTris/sec – 26FPS
• F4: 274MTris/sec – 16FPS
• F5: mode not available
• F6: mode not available

8 millions de triangles – 800 tri/instance

NVIDIA GeForce 8800 GTX – Forceware 169.38 XP32

• F1: 190MTri/sec – 25FPS
• F2: 190MTri/sec – 25FPS
• F3: 205MTri/sec – 27FPS
• F4: 213MTri/sec – 28FPS
• F5: 205MTri/sec – 27FPS
• F6: 152MTri/sec – 20FPS

ATI Radeon HD 3870 – Catalyst 8.2 XP32

• F1: 251MTris/sec – 33FPS
• F2: 236MTris/sec – 31FPS
• F3: 297MTris/sec – 39FPS
• F4: 251MTris/sec – 33FPS
• F5: mode not available
• F6: mode not available

2 millions de triangles – 200 tri/instance

NVIDIA GeForce 8800 GTX – Forceware 169.38 XP32

• F1: 47MTri/sec – 25FPS
• F2: 47MTri/sec – 25FPS
• F3: 57MTri/sec – 30FPS
• F4: 131MTri/sec – 69FPS
• F5: 167MTri/sec – 88FPS
• F6: 148MTri/sec – 78FPS

ATI Radeon HD 3870 – Catalyst 8.2 XP32

• F1: 47MTris/sec – 25FPS
• F2: 59MTris/sec – 31FPS
• F3: 74MTris/sec – 39FPS
• F4: 112MTris/sec – 59FPS
• F5: mode not available
• F6: mode not available

720,000 triangles – 72 tri/instance

NVIDIA GeForce 8800 GTX – Forceware 169.38 XP32

• F1: 17MTri/sec – 25FPS
• F2: 17MTri/sec – 25FPS
• F3: 20MTri/sec – 30FPS
• F4: 47MTri/sec – 69FPS
• F5: 60MTri/sec – 88FPS
• F6: 53MTri/sec – 78FPS

ATI Radeon HD 3870 – Catalyst 8.2 XP32

• F1: 17MTris/sec – 25FPS
• F2: 21MTris/sec – 31FPS
• F3: 26MTris/sec – 39FPS
• F4: 40MTris/sec – 59FPS
• F5: mode not available
• F6: mode not available

180000 triangles – 18 tri/instance

NVIDIA GeForce 8800 GTX – Forceware 169.38 XP32

• F1: 4MTri/sec – 25FPS
• F2: 4MTri/sec – 25FPS
• F3: 5MTri/sec – 30FPS
• F4: 11MTri/sec – 69FPS
• F5: 15MTri/sec – 89FPS
• F6: 13MTri/sec – 79FPS

ATI Radeon HD 3870 – Catalyst 8.2 XP32

• F1: 4MTris/sec – 25FPS
• F2: 5MTris/sec – 31FPS
• F3: 6MTris/sec – 39FPS
• F4: 10MTris/sec – 59FPS
• F5: mode not available
• F6: mode not available

Quick results analysis:

• we now understand why NVIDIA has called the technique using persistent vertex attributes “Pseudo-Instancing” (key F4). OpenGL glDrawElements() function is extremly fastand persistent vertex attributes require less overhead than uniforms to be passed to vertex shader. Both coupled together give this performance boost.
• benefit of real hardware geometry instancing is mostly visible with few triangles per instance.
• when there are many triangles per instance (1,800), the hardware implementation of glDrawElements() seems to be more efficient (twice!) on RV670 GPU than on G80.

Conclusion

From the results, hardware geometry instancing isn’t the kill-feature I expected. I find that very weird since the différence between 10000 render-calls with glDrawElements and 25 render-calls with glDrawElementsInstancedEXT is not verx important. Seems the instancing management (gl_InstanceID variable in the vertex shader) is a GPU-cycle eater!What a pity ATI hasn’t implemented yet geometry instancing in the Catalyst drivers. I’d be very curious to test hardware GI with a RV670.

Dryad is a tree gnenrator. It’s an OpenGL application and is available for Windows and MacOS X. Dryad allows to select a tree from a space called “the space of all trees” (in the right side of the app). The tree is created by interpolation between all trees that lie near the mouse. Pay attention because Dryad is very memory-consuming and 2 Gb of ram is recommended.

Once you have select your tree, a click on the gearing icon displays the tree parameters. You can customize everything: trunk, leaves, branches.

On the following image, I reduced the number of leaves and slightly incurved the upper branches.

My adjustments end up to :

Dryad exports your creation in an OBJ file. The one of the previous image is a huge 62Mb OBJ file, ouch! The OBJ file is properly generated and comes with its materials file. 62Mb is too big, and after a few adjustments, I get a 2Mb OBJ file with approximately 24000 faces. Okay now let’s load it in HyperView3D:

Now the problem now is that Y and Z coordinates are reversed. But HyperView3D has a little function to solve this problem: the swap of Y and Z coordinates. Because we encouter this problem time to time, this little function is useful…

For those who want to play with that OBJ file, you can grab it here: Dryad_Tree.zip.

Conclusion: Dryad is a handy utility for trees generation but requires a powerful computer. The OBJ export makes it possible to exploit the trees in all 3D applications that can load this standard format (like Demoniak3D for instance!).

Here is a sum-up of the next GPGPU: far more important than you think. Think 10x a CPU’s performance.

This article discusses about the use of GPU for non-graphical purposes or GPGPU (General Purpose (computation) on Graphics Processing Units). The author talks essentially about ATI 3870 X2 and the FireStream 9170 Stream Processor but don’t forget that NVIDIA has also the same kind of products with the Geforce 8 or Tesla. ATI’s Radeon HD 3870 X2 can hit around 1TFLOPS (one trillion floating-point operations per second), in contrast, a high-end quad-core CPU can push out around 60GFLOPS, or one-sixteenth the amount of floating-point power.

To program the GPU for non graphical rendering, you can use the The FireStream SDK (Software Development Kit) for ATI cards that gives the developer low-level access to the workings of the GPU. With NVIDIA boards, you can use CUDA to perform equivalent tasks.

And the final sentence:

”So the next time you look at the Radeon HD 3870 or NVIDIA GeForce 8800 GT in your machine, remember that it’s more than just a graphics card; it’s a floating-point monster that will increasingly be used for non-graphical tasks.”

Related Links:

AMD Pioneers Stream Computing on Graphics Processor Units

Stream Computing FAQ

AMD FireStream 9170: Industry’s First GPU with Double-Precision Floating Point

Stream Computing: SDK et RV670

NVIDIA CUDA homepage

CUDA @ oZone3D.Net forums

CUDA et OpenGL @ oZone3D.Net forums

CUDA en pratique @ oZone3D.Net forums