opengl光照之漫反射逐顶点渲染与逐像素渲染
1，逐顶点渲染：模型中有多少个顶点就计算多少次，这种方式比较节约系统资源，但效果比较粗糙
2，逐像素渲染：这种方式计算量特别大，有多少个像素就计算多少次，但是效果会很好
逐顶点渲染漫反射光照效果
顶点shader
attribute vec3 pos;//顶点坐标
attribute vec2 texcoord;//纹理坐标
attribute vec3 normal;//法线坐标
uniform mat4 M;//模型变换矩阵
uniform mat4 P;//投影矩阵
uniform mat4 V;//摄像机观察矩阵
uniform mat4 NM;//normalMatrix 将法线转换到世界坐标系或者视口坐标系的矩阵
uniform vec3 U_LightPos;//光源位置 本例只讨论平行光
uniform vec4 U_DiffuseLightColor;//漫反射光的颜色
uniform vec4 U_DiffuseMaterial;//漫反射光的材质
varying vec4 V_DiffuseColor;//最终光照颜色
void main()
{
vec3 L=U_LightPos;//平行光的反射方向 ,方向是由模型上的入射点指向光源，本例所有光线都是平行的
//归一化处理
L=normalize(L);
//将法线转换到世界坐标系或视口坐标系，这步很重要，否则得到的光照是不正确的
vec3 n=normalize(mat3(NM)*normal);
//得到漫反射光的强度 在 0.0和 L,n的点积之间取最大值 点积就是两向量分量分别相乘然后相加
float diffuseIntensity=max(0.0,dot(L,n));
//漫反射光的最终计算方式
V_DiffuseColor=U_DiffuseLightColor*U_DiffuseMaterial*diffuseIntensity;
gl_Position=P*V*M*vec4(pos,1.0);
}
这种情况下 fs非常简单
uniform vec4 U_AmbientLightColor;//环境光颜色
uniform vec4 U_AmbientMaterial;//环境光材质
varying vec4 V_DiffuseColor;
void main()
{
vec4 ambientColor=U_AmbientLightColor*U_AmbientMaterial;
gl_FragColor=ambientColor+V_DiffuseColor;//最终渲染像素=环境光+漫反射光
}逐像素渲染漫反射光照效果
将光照计算从顶点shader放到了片段shader
顶点shader
attribute vec3 pos;
attribute vec2 texcoord;
attribute vec3 normal;
uniform mat4 M;
uniform mat4 P;
uniform mat4 V;
uniform mat4 NM;
varying vec3 V_Normal; //法线
void main()
{
V_Normal=mat3(NM)*normal;//将法线坐标转换到世界坐标系
gl_Position=P*V*M*vec4(pos,1.0);
}uniform vec3 U_LightPos;//光源位置
uniform vec4 U_AmbientLightColor;//环境光颜色
uniform vec4 U_AmbientMaterial;//环境光材质
uniform vec4 U_DiffuseLightColor;//漫反射光颜色
uniform vec4 U_DiffuseMaterial;//漫反射光材质
varying vec3 V_Normal;//顶点shader中已转换到世界坐标系或者视口坐标系的法线,不转换就得不到正确的光照
void main()
{
//计算环境光
vec4 ambientColor=U_AmbientLightColor*U_AmbientMaterial;
//计算漫反射光
//入射光向量
vec3 L=U_LightPos;//此次只考虑平行光
L=normalize(L);
//法线坐标归一化
vec3 n=normalize(V_Normal);
//计算漫反射光照强度
float diffuseIntensity=max(0,dot(L,n));
//最终漫反射光照颜色
vec4 diffuseColor=U_DiffuseLightColor*U_DiffuseMaterial*diffuseIntensity;
//最终渲染像素值
gl_FragColor=ambientColor+diffuseColor;
}其中很关键的一点
uniform mat4 NM;的计算 也就是normalMatrix的计算方式=模型矩阵的逆矩阵的转置
glm::mat4 modelMatrix = glm::translate(0.0f,0.0f,-3.0f);
glm::mat4 projectionMatrix = glm::perspective(50.0f, 800.0f / 600.0f, 0.1f, 1000.0f);
//法线矩阵=模型矩阵的逆矩阵的转置
glm::mat4 normalMatrix = glm::inverseTranspose(modelMatrix); 完整的渲染函数
#include
#include "glew.h"
#include
#include
#include "utils.h"
#include "GPUProgram.h"
#include "ObjModel.h"
#include "FBO.h"
#include "FullScreenQuad.h"
#include "Glm/glm.hpp"
#include "Glm/ext.hpp"
#pragma comment(lib,"opengl32.lib")
#pragma comment(lib,"glew32.lib")
LRESULT CALLBACK GLWindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch (msg)
{
case WM_CLOSE:
PostQuitMessage(0);
break;
}
return DefWindowProc(hwnd,msg,wParam,lParam);
}
INT WINAPI WinMain(_In_ HINSTANCE hInstance, _In_opt_ HINSTANCE hPrevInstance, _In_ LPSTR lpCmdLine, _In_ int nShowCmd)
{
WNDCLASSEX wndClass;
wndClass.cbClsExtra = 0;
wndClass.cbSize = sizeof(WNDCLASSEX);
wndClass.cbWndExtra = 0;
wndClass.hbrBackground = NULL;
wndClass.hCursor = LoadCursor(NULL,IDC_ARROW);
wndClass.hIcon = NULL;
wndClass.hIconSm = NULL;
wndClass.hInstance = hInstance;
wndClass.lpfnWndProc=GLWindowProc;
wndClass.lpszClassName = L"OpenGL";
wndClass.lpszMenuName = NULL;
wndClass.style = CS_VREDRAW | CS_HREDRAW;
ATOM atom = RegisterClassEx(&wndClass);
HWND hwnd = CreateWindowEx(NULL, L"OpenGL", L"RenderWindow", WS_OVERLAPPEDWINDOW, 100, 100, 800, 600, NULL, NULL, hInstance, NULL);
HDC dc = GetDC(hwnd);
PIXELFORMATDESCRIPTOR pfd;
memset(&pfd, 0, sizeof(PIXELFORMATDESCRIPTOR));
pfd.nVersion = 1;
pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_TYPE_RGBA | PFD_DOUBLEBUFFER;
pfd.iLayerType = PFD_MAIN_PLANE;
pfd.iPixelType = PFD_TYPE_RGBA;
pfd.cColorBits = 32;
pfd.cDepthBits = 24;
pfd.cStencilBits = 8;
int pixelFormatID = ChoosePixelFormat(dc, &pfd);
SetPixelFormat(dc,pixelFormatID,&pfd);
HGLRC rc = wglCreateContext(dc);
wglMakeCurrent(dc, rc);
glewInit();//初始化环境
//加载shader并编译
GPUProgram gpuProgram;
//逐顶点渲染shader
//gpuProgram.AttachShader(GL_VERTEX_SHADER, "Debug/res/shader/diffuse_vs.vs");
//gpuProgram.AttachShader(GL_FRAGMENT_SHADER, "Debug/res/shader/diffuse_vs.fs");
//逐像素渲染shader
gpuProgram.AttachShader(GL_VERTEX_SHADER, "Debug/res/shader/diffuse_fs.vs");
gpuProgram.AttachShader(GL_FRAGMENT_SHADER, "Debug/res/shader/diffuse_fs.fs");
gpuProgram.Link();
//获取shader中变量的引用 并将属性名，产生的引用id放入map
gpuProgram.DetectAttribute("pos");
gpuProgram.DetectAttribute("texcoord");
gpuProgram.DetectAttribute("normal");
gpuProgram.DetectUniform("M");
gpuProgram.DetectUniform("V");
gpuProgram.DetectUniform("P");
gpuProgram.DetectUniform("NM");
gpuProgram.DetectUniform("U_AmbientLightColor");
gpuProgram.DetectUniform("U_AmbientMaterial");
gpuProgram.DetectUniform("U_DiffuseLightColor");
gpuProgram.DetectUniform("U_DiffuseMaterial");
gpuProgram.DetectUniform("U_LightPos");
//加载并解析模型
ObjModel model;
model.Init("Debug/res/model/Sphere.obj");
float identity[] = {
1.0f,0,0,0,
0,1.0f,0,0,
0,0,1.0f,0,
0,0,0,1.0f
};
float ambientLightColor[] = {0.4f,0.4f,0.4f,1.0f};//环境光颜色
float ambientMaterial[] = { 0.2f,0.2f,0.2f,1.0f };//环境光材质
float diffuseLightColor[] = { 1.0f,1.0f,1.0f,1.0f };//漫反射光颜色
float diffuseMaterial[] = { 0.8f,0.8f,0.8f,1.0f };//漫反射光材质
float lightPos[] = {1.0f,1.0f,0.0f};
glm::mat4 modelMatrix = glm::translate(0.0f,0.0f,-3.0f);
glm::mat4 projectionMatrix = glm::perspective(50.0f, 800.0f / 600.0f, 0.1f, 1000.0f);
//法线矩阵=模型矩阵的逆矩阵的转置
glm::mat4 normalMatrix = glm::inverseTranspose(modelMatrix);
glClearColor(41.0f/255.0f, 71.0f/255.0f, 121.0f / 255.0f, 1.0f);
ShowWindow(hwnd, SW_SHOW);
UpdateWindow(hwnd);
MSG msg;
while (true)
{
if (PeekMessage(&msg,NULL,NULL,NULL,PM_REMOVE))
{
if (msg.message==WM_QUIT)
{
break;
}
TranslateMessage(&msg);
DispatchMessage(&msg);
}
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glUseProgram(gpuProgram.mProgram);
glUniformMatrix4fv(gpuProgram.GetLocation("M"), 1,GL_FALSE, glm::value_ptr(modelMatrix));
glUniformMatrix4fv(gpuProgram.GetLocation("V"), 1, GL_FALSE, identity);
glUniformMatrix4fv(gpuProgram.GetLocation("P"), 1, GL_FALSE, glm::value_ptr(projectionMatrix));
glUniformMatrix4fv(gpuProgram.GetLocation("NM"), 1, GL_FALSE, glm::value_ptr(normalMatrix));
glUniform4fv(gpuProgram.GetLocation("U_AmbientLightColor"), 1,ambientLightColor);
glUniform4fv(gpuProgram.GetLocation("U_AmbientMaterial"), 1, ambientMaterial);
glUniform4fv(gpuProgram.GetLocation("U_DiffuseLightColor"), 1, diffuseLightColor);
glUniform4fv(gpuProgram.GetLocation("U_DiffuseMaterial"), 1, diffuseMaterial);
glUniform3fv(gpuProgram.GetLocation("U_LightPos"), 1, lightPos);
model.Bind(gpuProgram.GetLocation("pos"), gpuProgram.GetLocation("texcoord"), gpuProgram.GetLocation("normal"));
model.Draw();
glUseProgram(0);
glFinish();
SwapBuffers(dc);
}
return 0;
}