CUDA Rasterizer

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University of Pennsylvania, CIS 565: GPU Programming and Architecture, Project 4

• LINSHEN XIAO
• Tested on: Windows 10, Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz, 16.0GB, NVIDIA GeForce GTX 970M (Personal computer)

Overview

In this project, I used CUDA to implement a simplified rasterized graphics pipeline, similar to the OpenGL pipeline. I have implemented vertex shading, primitive assembly, rasterization, fragment shading, and a framebuffer.

Features

• Basic Lambert and Blinn-Phong
• Line & Point rasterization
• Backface culling
• SSAA
• Other render style(painted style)
• Bilinear texture filtering
• Perspective correct texture coordinates

Results

Rotating Duck

Basic Lambert and Blinn shading

Duck with texture and point light	+Blinn-Phong	+Ambient light

Basic Normal and depth shading

Duck with texture as color	Duck with normal as color	Duck with depth as color

Line and point rasterization

Duck rasterized with triangles	Duck rasterized with lines	Duck rasterized with dots

Backface culling

Duck rasterized with front faces	Duck rasterized with back faces

SSAA

No SSAA	SSAA*2	SSAA*4

Let's have a closer look:

No SSAA	SSAA*2	SSAA*4

Painted style render

Original Duck	"Painted style" Duck

UV texture mapping with bilinear texture filtering and perspective correct texture coordinates

Original Checkerboard	+Perspective correct texture coordinates	+Bilinear texture filtering

Let's have a closer look:

No Bilinear texture filtering	+Bilinear texture filtering	+SSAA*2

Performance Analysis

Pipeline	No Backface Culling	Backface Culling
Rasterizer	1716.314	1375.803
Fragment Shader	681.287	688.537
Framebuffer	103.308	103.252
Primitive Assembly	28.59	28.632
Vertex Assembly and Shader	11.014	11.004

Here we take the duck scene as an example. We can clearly see that rasterizer use most of the time, as there are lots of computation in this process, to check if the pixel of the bounding box lies inside the triangle, depth test and compute the interpolated texture coordinates and normal and so on. The render function in fragment shader also has some amount of computation for the computation for the color decided by normal, light direction and texture color.

We can see that backface culling did save time in rasterizer part. As the backface triangles are ingnored in the process, the performance did improved a bit.

Pipeline	No bilinear texture filtering and perspective correctness	With bilinear texture filtering and perspective correctness
Rasterizer	1716.314	3049.726
Fragment Shader	681.287	717.102
Framebuffer	103.308	105.129
Primitive Assembly	28.59	28.857
Vertex Assembly and Shader	11.014	11.101

We can see that bilinear texture filtering and perspective correctness did take more time in rasterizer and fragment shader part, for the computation of perspective correct texture coordinates and averanging texture color for bilinear texture filtering did take more time than the orginal method.

Credits

• tinygltfloader by @soyoyo
• glTF Sample Models
• Line drawing
• Backface culling