The document discusses techniques for snow accumulation and generation in 3D graphics. It describes using shadow mapping to accumulate snow based on a depth map and vertex lighting calculations. It also covers randomly positioning snow particles and rendering them with point sprites along with particle animation. Fog effects are achieved using GLSL fog shaders.

1. SNOW ACCUMULATION AND
GENERATION
Yuanhui

2. MAIN PARTS
 Particle Rendering for Snow Generation
 Shadow Mapping for Snow Accumulation
 Fog Effect

3. SNOW ACCUMULATION
 Rendering Depth Map
 From the view of the sky with orthographic camera
 Render depth values to texture

4. SNOW ACCUMULATION
 Rendering Object
 Shadow testing: not exposed when depth larger than
depth map value
 Read depth map value
 VL = Ms * Mp * Mv * Mm * V
 VL projected vertex from light source
 Ms scale matrix (-1, 1) to (0, 1)
 Mp light source projection
 Mv light source view from world
 Mm model to world
 V vertices

5. SNOW ACCUMULATION
 Incline Coefficient
 dot(Y, normal)
http://http.download.nvidia.com/developer/SDK/Individual_Samples/
DEMOS/Direct3D9/src/SnowAccumulation/Docs/SnowAccumulation.pdf

6. SNOW GENERATION
 Random Position
 Particles Rendering
 glEnable(GL_POINT_SPRITE)
 glEnable(GL_VERTEX_PROGRAM_POINT_SIZE)
 gl_PointSize
 GL_POINTS
 Particle Animation
 calculate alpha (vertex shader)

7. FOG EFFECT
http://www.ozone3d.net/tutorials/glsl_fog/p02.php

8. REFERENCE
 http://http.download.nvidia.com/developer/SDK/Indi
vidual_Samples/DEMOS/Direct3D9/src/SnowAccu
mulation/Docs/SnowAccumulation.pdf
 https://graphics.stanford.edu/wikis/cs248-11-
winter/CS_248%3A_Interactive_Computer_Graphic
s?action=AttachFile&do=get&target=OpenGLParticl
es.pdf
 http://www.ozone3d.net/tutorials/glsl_fog
 http://www.opengl-tutorial.org/intermediate-
tutorials/tutorial-16-shadow-mapping/

9. THANKS!