CUDA Rasterizer

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

• Ziwei Zong
• Tested on: Windows 10, i7-5500 @ 2.40GHz 8GB, GTX 950M (Personal)

Overview

A Cuda rasterize with texture mapping, smooth tessellation and displacement mapping.

Video Demo

Controls

KEY/Mouse	Function	Demo Image
Left Mouse	Rotate	[pic]
Middle Mouse	Zoom	[pic]
Right Mouse	Move	[pic]
Key '0'	Wireframe only	[pic]
Key '1'	Color	[pic]
Key 'w'	turn wireframe on/off	[pic]
Key 't'	turn texture on/off	[pic]
Key 'n'	normal testing	[pic]
Key 'd'	turn displacement mapping on/off	[pic]
Key 'm'	use middle point tessellation method	[pic]
Key 'c'	use curved PN tessellation method	[pic]
Key Up/Down	increase/reduce tessellation level	[pic]
Key Left/Right	increase/reduce texture repeat	[pic]

Features

Tessellation

Middle Point Tessellation

This method is very straight forward. For each triangle (primitive), find middle points on each edge, then tessellate one triangle into four triangles.

original geometry	Middle Point Tessellation	Curved PN Tessellation

Smooth Tessellation (Curved PN Method)

Using cubic Bezier interpolation to calculate tessellated points and normals. Each triangle is tessellated into nine triangles.

original geometry	after tessellated using cubic Bezier interpolation

Displacement Mapping

Tessellation level	without displacement map	with displacement map

	5			|![](img/tess_5_w.PNG)		|![](img/tess_5_d.PNG)

Tessellation level	after displacement map	normal testing for displacement map

	8			|![](img/tess_8_.PNG)		|![](img/tess_8n.PNG)

Texture Mapping

Bilinear Texture Filtering:

without texture filtering	with bilinear texture filtering

Texture Repeat:

    2.4     |        5.8     | 15.8

:--------------:|:--------------:|:--------------: ||

Interpolation

without normal&color interpolation	with normal&color interpolation

Performance Analysis

Pipeline Optimization

Considering that after loading the geometry, there's no need to redo primitive assembly and tessellation within each frame when the tessellation level dosn't change. Therefore, I only do vertex shader and primitive assembly once and take them out of the main loop. Instead, all vertices' ndc value and window positions are updated based on current transformation matrices (view, projection, window...) in each frame.

The pipeline workflow is shown below.

• Analysis for Tessellation

Tested suzzane.obj (968 faces, 2904 vertices) with only tessellation.

|

• Analysis for Tessellation and Displacement Map

Tested plane.obj (2 faces, 4 vertices) with tessellation,texture mapping and displacement mapping.

|

Both two cases above shows that the new pipeline out performs the previouse one when the tessellation level is high.

And another interesting thing is that when tessellation level is low, it actually goes faster by increasing the tessellation level for both two cases. My guess is that when tessellation level goes a bit higher, there are more threads dealing with smaller AABBs. Thus the same amount of work is paralled as more smaller tasks. When the triangle counts is below certain amount, it trades off the increment of triangles and threads very well.

Obj Analysis

References

Mouse Control

• http://www.opengl-tutorial.org/beginners-tutorials/tutorial-6-keyboard-and-mouse/
• http://r3dux.org/2011/05/simple-opengl-keyboard-and-mouse-fps-controls/
• https://github.com/LWJGL/lwjgl3-wiki/wiki/2.6.3-Input-handling-with-GLFW

Tessellation

• http://prideout.net/blog/?p=48
• http://www.cs.cmu.edu/afs/cs/academic/class/15418-s12/www/lectures/25_micropolygons.pdf
• http://www.eecs.berkeley.edu/~sequin/CS284/PROJ_12/Brandon/Smooth%20GPU%20Tessellation.pdf
• http://http.developer.nvidia.com/GPUGems2/gpugems2_chapter07.html
• http://perso.telecom-paristech.fr/~boubek/papers/PhongTessellation/PhongTessellation.pdf

Texture Mapping

• https://en.wikipedia.org/wiki/Bilinear_interpolation

Displacement Map

• https://www.opengl.org/wiki/Calculating_a_Surface_Normal

Obj Files

• http://www.kunzhou.net/tex-models.htm

To Do...

1. cannot tessellate cow.obj
2. cannot open sponza.obj
3. seperate textures