Implementation: LightedTexCube

Overview 

In previous examples, we saw that Position, Color, Texture data were sent to draw cubes. In this post we  will discuss how to implement  Phong lighting models and other lights such as Directional, Point and Spot Lights. For this surface normals needs to be sent as VBO data. They look as shown at the bottom. They look elongated because aspect ratio is not applied.

Details

System  class diagram

LightedTexCube derives from TexturedCube class. It overrides mesh with an instance of CubeMesh to generate geometry. 

LightedTexCube

LightedTexCube is derived from TexturedCube class. It illuminates the textured cube as per settings done in the light parameter. Utility class gLightingUtil is used for lighting related settings.

Members

Name	Description
light	An instance of LightingUtil. It contains settings for illumination.

Methods

Name	Description
Init	This method overrides the base class Init method to load texture.  Generates the vertices data consisting of surface normals in non indexed mode and later sets them up in VBO buffer.  It also passes an input to use BlinnPhong or Phong illumination and also type of light source as defined by LightSource enum.
UpdateUniforms	This method overrides the base class UpdateUniforms method. Firs t it updates  "cameraposition" uniform. Next it updates lighting related uniforms by calling Updateshader method on light. Finally it c alls base class UpdateUniforms method to send rest.
vertexShaderSource	This method overrides the base class vertexShaderSource method. It returns the vertex shader code to render the cube object.
fragmentShaderSource	This method overrides the base class fragmentShaderSource method. It returns the fragment shader code to render the cube object based on light source type.

MaterialInfo

This class contains information about a single Material obtained after parsing a mtl file. This information includes  Ambient, Diffuse, Specular Colors and Texture information etc.  Note that a mtl file can have multiple Materials applicable to a range of meshes.

These are stored in LightingUtil object discussed below.

Members

Name	Description
name	Name of the material.
ambientColor	Contains ambient color
diffuseColor	Contains Diffuse color
specularColor	Contains Specular color
Shininess	Contains shininess value

LightSrcInfo

This class contains information about the light source and viewer position for lighting calculations.

These are stored in GenericObj object discussed below. 

Members

Name	Description
src	Contains light source type information. It has to be one of LightSourceType
name	Name of the light source.
ambientCoefficient ambientColor	Contains Ambient Coefficient and color
diffuseCoefficient diffuseColor	Contains Diffuse Coefficient and color
specularColor specularCoefficient	Contains Specular Coefficient and color
blinn	Contains boolean value to indicate to render blinn-phong(true) or phong(false)  lighting.
position	Contains light position  information required for basic, point and spot lighting.
direction	Contains direction information required for directional lighting.
attconstant attlinear attquadratic	Contains light attenuation information required for point and spot lighting.
spotlightinner spotlightouter	Contains light angle information required for spot lighting.

LightingUtil

It defines illumination properties of the light source and reflection properties of the material in the light and material members.

Members

Name	Description
material	An instance of Material class. It contains settings of the material property for reflection.
light	An instance of LightSrcInfo class. It contains settings for illumination.

Methods

Name	Description
UpdateShader	Updates the uniforms that contains copies of the information stored in light and material members.

Output

The output looks as shown below.