【OpenGL】ADS光照模型

ADS是Ambient、Diffuse、Specular意思，用环境光、漫反射、高光反射进行渲染物体。

uniform vec3 vAmbientMaterial;
uniform vec3 vAmbientLight;
vec3 vAmbientColor = vAmbientMaterial * vAmbientLight;  //即环境光颜色 * 环境光亮度 得到环境光颜色

uniform vec3 vDiffuseMaterial;
uniform vec3 vDiffuseLight;
float fDotProduct = max(0.0, dot(vNormal, vLightDir);
vec3 vDiffuseColor = vDiffuseMaterial * vDiffuseLight * fDotProduct;

uniform vec3 vSpecularMaterial;
uniform vec3 vSpecularLigth;
float shininess = 128.0;
vec3 vReflection = reflect(-vLightDir, vEyeNormal);
float EyeReflectionAngle = max(0.0, dot(vEyeNormal, vReflection);
fSpec = pow(EyeReflectionAngle * shininess);
vec3 vSpecularColor = vSpecularLight * vSpecularMaterial * fSpec;

以上三段代码分别是环境光、漫反射、高光反射内容。具体代码如下：

// ADS Point lighting Shader
// Vertex Shader
// Richard S. Wright Jr.
// OpenGL SuperBible
#version 130

// Incoming per vertex... position and normal
in vec4 vVertex;
in vec3 vNormal;

// Set per batch
uniform vec4    ambientColor;
uniform vec4    diffuseColor;	
uniform vec4    specularColor;

uniform vec3	vLightPosition;
uniform mat4	mvpMatrix;
uniform mat4	mvMatrix;
uniform mat3	normalMatrix;

// Color to fragment program
smooth out vec4 vVaryingColor;

void main(void) 
    { 
    // Get surface normal in eye coordinates
    vec3 vEyeNormal = normalMatrix * vNormal;

    // Get vertex position in eye coordinates
    vec4 vPosition4 = mvMatrix * vVertex;
    vec3 vPosition3 = vPosition4.xyz / vPosition4.w;

    // Get vector to light source
    vec3 vLightDir = normalize(vLightPosition - vPosition3);

    // Dot product gives us diffuse intensity
    float diff = max(0.0, dot(vEyeNormal, vLightDir));

    // Multiply intensity by diffuse color, force alpha to 1.0
    vVaryingColor = diff * diffuseColor;

    // Add in ambient light
    vVaryingColor += ambientColor;


    // Specular Light
    vec3 vReflection = normalize(reflect(-vLightDir, vEyeNormal));
    float spec = max(0.0, dot(vEyeNormal, vReflection));
    if(diff != 0) {
        float fSpec = pow(spec, 128.0);
        vVaryingColor.rgb += vec3(fSpec, fSpec, fSpec);
	}


    // Don't forget to transform the geometry!
    gl_Position = mvpMatrix * vVertex;
    }

// ADS Point lighting Shader
// Fragment Shader
// Richard S. Wright Jr.
// OpenGL SuperBible
#version 130

out vec4 vFragColor;
smooth in vec4 vVaryingColor;

void main(void)
   { 
   vFragColor = vVaryingColor;
   }

// DiffuseLight.cpp
// OpenGL SuperBible
// Demonstrates simple diffuse lighting
// Program by Richard S. Wright Jr.
#pragma comment(lib,"gltools.lib")
#include <GLTools.h>	// OpenGL toolkit
#include <GLMatrixStack.h>
#include <GLFrame.h>
#include <GLFrustum.h>
#include <GLGeometryTransform.h>
#include <StopWatch.h>

#include <math.h>
#ifdef __APPLE__
#include <glut/glut.h>
#else
#define FREEGLUT_STATIC
#include <GL/glut.h>
#endif


GLFrame             viewFrame;
GLFrustum           viewFrustum;
GLTriangleBatch     sphereBatch;
GLMatrixStack       modelViewMatrix;
GLMatrixStack       projectionMatrix;
GLGeometryTransform transformPipeline;
GLShaderManager     shaderManager;

GLuint	ADSLightShader;		// The diffuse light shader
GLint	locAmbient;			// The location of the ambient color
GLint   locDiffuse;			// The location of the diffuse color
GLint   locSpecular;		// The location of the specular color
GLint	locLight;			// The location of the Light in eye coordinates
GLint	locMVP;				// The location of the ModelViewProjection matrix uniform
GLint	locMV;				// The location of the ModelView matrix uniform
GLint	locNM;				// The location of the Normal matrix uniform


// This function does any needed initialization on the rendering
// context. 
void SetupRC(void)
{
	// Background
	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);

	glEnable(GL_DEPTH_TEST);
	glEnable(GL_CULL_FACE);

	shaderManager.InitializeStockShaders();
	viewFrame.MoveForward(4.0f);

	// Make the sphere
	gltMakeSphere(sphereBatch, 1.0f, 26, 13);

	ADSLightShader = shaderManager.LoadShaderPairWithAttributes("ADSGouraud.vp", "ADSGouraud.fp", 2, GLT_ATTRIBUTE_VERTEX, "vVertex",
		GLT_ATTRIBUTE_NORMAL, "vNormal");

	locAmbient = glGetUniformLocation(ADSLightShader, "ambientColor");
	locDiffuse = glGetUniformLocation(ADSLightShader, "diffuseColor");
	locSpecular = glGetUniformLocation(ADSLightShader, "specularColor");
	locLight = glGetUniformLocation(ADSLightShader, "vLightPosition");
	locMVP = glGetUniformLocation(ADSLightShader, "mvpMatrix");
	locMV = glGetUniformLocation(ADSLightShader, "mvMatrix");
	locNM = glGetUniformLocation(ADSLightShader, "normalMatrix");
}

// Cleanup
void ShutdownRC(void)
{

}


// Called to draw scene
void RenderScene(void)
{
	static CStopWatch rotTimer;

	// Clear the window and the depth buffer
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	modelViewMatrix.PushMatrix(viewFrame);
	modelViewMatrix.Rotate(rotTimer.GetElapsedSeconds() * 10.0f, 0.0f, 1.0f, 0.0f);

	GLfloat vEyeLight[] = { -100.0f, 100.0f, 100.0f };
	GLfloat vAmbientColor[] = { 0.1f, 0.1f, 0.1f, 1.0f };
	GLfloat vDiffuseColor[] = { 0.0f, 0.0f, 1.0f, 1.0f };
	GLfloat vSpecularColor[] = { 1.0f, 1.0f, 1.0f, 1.0f };

	glUseProgram(ADSLightShader);
	glUniform4fv(locAmbient, 1, vAmbientColor);
	glUniform4fv(locDiffuse, 1, vDiffuseColor);
	glUniform4fv(locSpecular, 1, vSpecularColor);
	glUniform3fv(locLight, 1, vEyeLight);
	glUniformMatrix4fv(locMVP, 1, GL_FALSE, transformPipeline.GetModelViewProjectionMatrix());
	glUniformMatrix4fv(locMV, 1, GL_FALSE, transformPipeline.GetModelViewMatrix());
	glUniformMatrix3fv(locNM, 1, GL_FALSE, transformPipeline.GetNormalMatrix());
	sphereBatch.Draw();

	modelViewMatrix.PopMatrix();


	glutSwapBuffers();
	glutPostRedisplay();
}



void ChangeSize(int w, int h)
{
	// Prevent a divide by zero
	if (h == 0)
		h = 1;

	// Set Viewport to window dimensions
	glViewport(0, 0, w, h);

	viewFrustum.SetPerspective(35.0f, float(w) / float(h), 1.0f, 100.0f);

	projectionMatrix.LoadMatrix(viewFrustum.GetProjectionMatrix());
	transformPipeline.SetMatrixStacks(modelViewMatrix, projectionMatrix);
}

///
// Main entry point for GLUT based programs
int main(int argc, char* argv[])
{
	gltSetWorkingDirectory(argv[0]);

	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH | GLUT_STENCIL);
	glutInitWindowSize(800, 600);
	glutCreateWindow("ADS Lighting, Gouraud Shading");
	glutReshapeFunc(ChangeSize);
	glutDisplayFunc(RenderScene);

	GLenum err = glewInit();
	if (GLEW_OK != err) {
		fprintf(stderr, "GLEW Error: %s\n", glewGetErrorString(err));
		return 1;
	}

	SetupRC();
	glutMainLoop();
	ShutdownRC();
	return 0;
}