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Waylon Watson
Waylon Watson

Real-time 3d Rendering With Directx And Hlsl Pdf 11

Forward rendering works by rasterizing each geometric object in the scene. During shading, a list of lights in the scene is iterated to determine how the geometric object should be lit. This means that every geometric object has to consider every light in the scene. Of course, we can optimize this by discarding geometric objects that are occluded or do not appear in the view frustum of the camera. We can further optimize this technique by discarding lights that are not within the view frustum of the camera. If the range of the lights is known, then we can perform frustum culling on the light volumes before rendering the scene geometry. Object culling and light volume culling provide limited optimizations for this technique and light culling is often not practiced when using a forward rendering pipeline. It is more common to simply limit the number of lights that can affect a scene object. For example, some graphics engines will perform per-pixel lighting with the closest two or three lights and per-vertex lighting on three or four of the next closes lights. In traditional fixed-function rendering pipelines provided by OpenGL and DirectX the number of dynamic lights active in the scene at any time was limited to about eight. Even with modern graphics hardware, forward rendering pipelines are limited to about 100 dynamic scene lights before noticeable frame-rate issues start appearing.

real-time 3d rendering with directx and hlsl pdf 11

The obvious advantage with the deferred shading technique compared to forward rendering is that the expensive lighting calculations are only computed once per light per covered pixel. With modern hardware, the deferred shading technique can handle about 2,500 dynamic scene lights at full HD resolutions (1080p) before frame-rate issues start appearing when rendering only opaque scene objects.

Another disadvantage of deferred shading is that only a single lighting model can be simulated in the lighting pass. This is due to the fact that it is only possible to bind a single pixel shader when rendering the light geometry. This is usually not an issue for pipelines that make use of übershaders as rendering with a single pixel shader is the norm, however if your rendering pipeline takes advantage of several different lighting models implemented in various pixel shaders then it will be problematic to switch your rendering pipeline to use deferred shading.

Forward+ [2][3] (also known as tiled forward shading) [4][5] is a rendering technique that combines forward rendering with tiled light culling to reduce the number of lights that must be considered during shading. Forward+ primarily consists of two stages:

The VertexShaderOutput structure is used to pass the transformed vertex attributes to the pixel shader. The members that are named with a VS postfix indicate that the vector is expressed in view space. I chose to do all of the lighting in view space, as opposed to world space, because it is easier to work in view space coordinates when implementing the deferred shading and forward+ rendering techniques.

The Position and Direction properties are stored in both world space (with the WS postfix) and in view space (with VS postfix). Of course the Position variable only applies to point and spot lights while the Direction variable only applies to spot and directional lights. I store both world space and view space position and direction vectors because I find it easier to work in world space in the application then convert the world space vectors to view space before uploading the lights array to the GPU. This way I do not need to maintain multiple light lists at the cost of additional space that is required on the GPU. But even 10,000 lights only require 1.12 MB on the GPU so I figured this was a reasonable sacrifice. But minimizing the size of the light structs could have a positive impact on caching on the GPU and improve rendering performance. This is further discussed in the Future Considerations section at the end of this article.

The pixel shader for the forward rendering technique is slightly more complicated than the vertex shader. If you have read my previous article titled Texturing and Lighting in DirectX 11 then you should already be familiar with most of the implementation of this shader, but I will explain it in detail here as it is the basis of all of the rendering algorithms shown in this article.

The next phase is to count the number of pixels that were both marked in the previous phase and are inside the light volume. This is done by rendering the front faces of the light volume and counting the number of pixels that are both stencil marked in the previous phase and behind the front faces of the light volume. In this case, the pipeline state should be configured with:

The transparent pass for the deferred shading technique is identical to the forward rendering technique with alpha blending enabled. There is no new information to provide here. We will reflect on the performance of the transparent pass in the results section described later.

Even with very large lights, standard forward rendering is able to render 64 dynamic lights while still maintaining frame-rates below the maximum threshold of 30 FPS. With more than 512 lights, the frame time becomes immeasurably high.

The graph shows that tiled forward rendering is not well suited for rendering scenes with many large lights. Rendering 512 screen filling lights in the scene caused issues because the demo only accounts for having an average of 200 lights per tile. With 512 large lights the 200 light average was exceeded and many tiles simply appeared black.

Forward plus really shines when using many small lights. In this case we see that the light culling phase (orange line) is the primary bottleneck of the rendering technique. Even with over 16,000 lights, rendering opaque (blue line) and transparent (purple line) geometry fall below the minimum threshold to achieve a desired frame-rate of 60 FPS. The majority of the frame time is consumed by the light culling phase.

Even with small lights, deferred rendering requires many more draw calls to render the geometry of the light volumes. Using deferred rendering, each light volume must be rendered at least twice, the first draw call updates the stencil buffer and the second draw call performs the lighting equations. If the graphics platform is very sensitive to excessive draw calls, then deferred rendering may not be the best choice.

Similar to the scenario with large lights, when rendering only a few lights in the scene then all three techniques have similar performance characteristics. In this case, we must consider the additional memory requirements that are imposed by deferred and tiled forward rendering. Again, if GPU memory is scarce and there is no need for many dynamic lights in the scene then standard forward rendering may be a viable solution.

Another area of improvement for the tiled forward rendering technique would be to improve the accuracy of the light culling. Frustum culling could result in a light being considered to be contained within a tile when in fact no part of the light volume is contained in the tile.

Tiled forward rendering has a small initial overhead required to dispatch the light culling compute shader but the performance of tiled forward rendering with many dynamic lights quickly supasses the performance of both forward and deferred rendering. Tiled forward rendering requires a small amount of additional memory. Approximately 5.7 MB of additional storage is required to store the light index list and light grid using 1616 tiles at a screen resolution of 1280720. Tiled forward rendering requires that the target platform has support for compute shaders. It is possible to perform the light culling on the CPU and pass the light index list and light grid to the pixel shader in the case that compute shaders are not available but the performance trad-off might negate the benefit of performing light culling in the first place.

why clip space z for far plane in right hand system is -1 not 1, according to -basic-rendering/perspective-and-orthographic-projection-matrix/opengl-perspective-projection-matrixthe near plane mapped to -1 , far plan mapped to 1, i confused with it.

In this session, John McDonald will demonstrate a new, border-free technique for rendering Ptex datasets in real-time, on any OpenGL 4 (or Direct3D 11) capable consumer hardware. By jettisoning borders, the memory overhead of this method has even dropped below those of standard texture mapping. Session attendees will see a live Ptex demo running on commonly available consumer hardware. They will dive with John, deep into the guts of a complete, working OpenGL implementation.

The new Catzilla benchmark from Plastic is showcasing the latest rendering technology of their new engine. This rendering engine supports all the latest techniques, like physically correct lighting, depth-of-field, fur, volumetric and raymarching based effects, motion blur, and many other great-looking rendering effects. Using a pre-release of Nsight 3.0, the team was able to fix 3D API and rendering bugs, and optimize their engine to squeeze every possible cycle out of the GPU and system as a whole. Along with Jeff Kiel from the NVIDIA graphics developer tools team, they'll share their stories from the trenches to give the audience a good sense of how to take advantage of Nsight 3.0 for DirectX 11 and OpenGL 4.2 multi 3D API development.

OpenGL has changed rapidly with five releases in less than three years. This talk will discuss how the new improvements such as debug support, tessellation, and enhanced object-oriented support can improve your application. Additionally, this talk will cover what NVIDIA's latest features of path rendering and bindless graphics can provide.

Direct3D is a graphics application programming interface (API) for Microsoft Windows. Part of DirectX, Direct3D is used to render three-dimensional graphics in applications where performance is important, such as games. Direct3D uses hardware acceleration if it is available on the graphics card, allowing for hardware acceleration of the entire 3D rendering pipeline or even only partial acceleration. Direct3D exposes the advanced graphics capabilities of 3D graphics hardware, including Z-buffering,[1] W-buffering,[2] stencil buffering, spatial anti-aliasing, alpha blending, color blending, mipmapping, texture blending,[3][4] clipping, culling, atmospheric effects, perspective-correct texture mapping, programmable HLSL shaders[5] and effects.[6] Integration with other DirectX technologies enables Direct3D to deliver such features as video mapping, hardware 3D rendering in 2D overlay planes, and even sprites, providing the use of 2D and 3D graphics in interactive media ties.


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