University of Pennsylvania, CIS 565: GPU Programming and Architecture, Project 5
- Ziwei Zong
- Tested on:Google Chrome 46.0 on Windows 10, i7-5500 @ 2.40GHz 8GB, GTX 950M (Personal)
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{McGuire} Morgan McGuire, Williams College. Numerical Methods for Ray Tracing Implicitly Defined Surfaces (2014). PDF
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{iq-prim} Iñigo Quílez. Raymarching Primitives (2013). Shadertoy
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{iq-terr} Iñigo Quílez. Terrain Raymarching (2007). Article
- {iq-meng} Iñigo Quílez. Menger Sponge (2013). Shadertoy
Height Map
In line 11, define HeightMap as 1 to test this terrain feature:
#define HeightMap 1 //height: iChannel0
| Terrain with texture | Normal |
|---|---|
|
 |
| Distance Debug View | Iteration Number Debug View |
 |
 |
*Purple means less iteration and blue means more.
Menger Sponge
A fun thing about menger sponge is that by simply changing the threshold with time, there would be an interesting erosion effect, as shown above and live on Shadertoy.
Soft Shadow
| Soft Shadow | Sharp Shadow |
|---|---|
 |
 |
Ambient Occlusion
In line 12, define AO_Test as 1 to use the below scene:
#define AO_Test 1
| Without AO | With AO |
|---|---|
 |
 |
Test Scene
Iteration Number Debug View
| Naive Ray Marching | Sphere Tracing |
|---|---|
 |
 |
*Purple means less iteration and blue means more.
Precision and FPS
- Naive Ray Marching
| Max Iteration Number | 1000 | 1300 | 2000 | 4000 | 19000 |
|---|---|---|---|---|---|
| Precision | 0.02 | 0.015 | 0.01 | 0.005 | 0.001 |
| FPS | 60 | 52 | 38 | 20 | 4.3 |
- Sphere Tracing
| Max Iteration Number | 80000 | |||
|---|---|---|---|---|
| Precision | 1e-6 | 9.5e-7 | 9.0e-7 | 6.0e-7 |
| FPS | 60 | 12.5 | 7 | 6.8 |
As shown in the table, the FPS of naive ray marching drops off significantly due to the precision. A smaller the precision threshold means more iteration number and thus takes more time. However on the contrary, the sphere tracing method is not very sensitive to the precision.
As expected, the ray-casting step takes the longest time because all the iterations and interactions with objects are in this step. Same for the shadowing, since there are some iteration towards the light for each objects, it takes relatively longer time for shadowing than shading and ambient occlusion.