Unit 3: Color and Blending

Lighting and Material (Theory)

• To have a realistic rendering, we need these inputs
• Geometry
• Lighting
• Materials

• Material appearance parameters
• Intensity and shape of highlights
• Glossiness
• Color
• Spatial variation (i.e. Texture)

• Light sources
• For multiple light sources, use linearity
• We can add the solutions for two light sources
• We simply multiply the solution when we scale the light intensity



• Light intensity can be represented as function of distance

Types of Lights

Incoming Irradiance for Pointlights

Directional Lights

• A.K.A. Point lights that are infinitely far (like in real world)

Splotlights

• Spoltlight Geometry

Quantifying Reflection - BRDF

• Bidirectional Reflectance Distribution Function

• A function for measuring the reflection

• Ratio of light coming from one direction that gets reflected in another direction

Types of Materials

• When keeping l and v fixed, if rotation of surface around the normal does not change the reflection, the material is called isotropic

• Surfaces with strongly oriented microgeometry elements are anisotropic

Shaders in OpenGL

OpenGL Tutorial 5 - Shaders

https://www.youtube.com/watch?v=YaiSvKTOeRg&list=PLPaoO-vpZnumdcb4tZc4x5Q-v7CkrQ6M-&index=6

Shaders

As mentioned in the Hello Triangle chapter, shaders are little programs that rest on the GPU. These programs are run for each specific section of the graphics pipeline. In a basic sense, shaders are nothing more than programs transforming inputs to outputs.

https://learnopengl.com/Getting-started/Shaders

• Shaders are programs that run on GPU

• They are written in GLSL language
• It is similar to C lang
• Read more https://learnopengl.com/Getting-started/Shaders

• Vertex shader:
• Receives vertices coordinates and attributes (like vertex colors)
• Sets the positions of the vertex on screens
• Passes the other attributes (like vertex colors) to the fragment shader

• Fragment shader outputs colors

• This is the data structure of vertex (coordinates and colors info)
• Vertex Attribute Pointer scans the vertex array (VAO) and extract vertices attributes based on offset and stride info.

• Uniforms: universal variables that can be accessed by other shaders and the main function of the program w/o using the VAO
• It is used to adjust the shader by passing values (e.g. to scale up shapes)
• It is declared inside the shader source code and can be accessed from the program using glGetUniformLocation function that get the reference to it
• Then, we can set the uniform value using glUniform function (there are variations for this function based on the uniform data type)
• Read more https://registry.khronos.org/OpenGL-Refpages/gl4/

Textures in OpenGL

www.youtube.com

https://www.youtube.com/watch?v=u-00hjlfMKc&list=PLPaoO-vpZnumdcb4tZc4x5Q-v7CkrQ6M-&index=7

2D Textures

• A library called stb is used for importing textures

• Square pictures in powers of 2 are more optimzed than pictures with sizes of random number

• 2:00

Resources

Introduction to Computer Graphics (Lecture 13): Shading and materials

6.837: Introduction to Computer Graphics Autumn 2020 Many slides courtesy past instructors of 6.837, notably Fredo Durand and Barbara Cutler.

https://www.youtube.com/watch?v=GqK64s1WzwU&list=PLQ3UicqQtfNuBjzJ-KEWmG1yjiRMXYKhh&index=14

OpenGL Tutorial 5 - Shaders

https://www.youtube.com/watch?v=YaiSvKTOeRg&list=PLPaoO-vpZnumdcb4tZc4x5Q-v7CkrQ6M-&index=6

Shaders

As mentioned in the Hello Triangle chapter, shaders are little programs that rest on the GPU. These programs are run for each specific section of the graphics pipeline. In a basic sense, shaders are nothing more than programs transforming inputs to outputs.

https://learnopengl.com/Getting-started/Shaders