为什么是黑色的,因为缺少了一个.tga文件,代码里用glGenTexures(1, &textureID); 生成1个纹理对象
glBindTexture(GL_TEXTURE_2D, textureID); 创建和初始化二维纹理状态捆绑到纹理对象textureID上
LoadTGATexture("stone.tga", GL_LINEAR, GL_LINEAR, GL_CLAMP_TO_EDGE); 加载stone.tga图片并设置缩小过滤器过滤方式为线性、放大过滤器过滤方式为线性以及纹理环绕模式。
bool LoadTGATexture(const char *szFileName, GLenum minFilter, GLenum magFilter, GLenum wrapMode); 该函数是完整地对纹理状态进行设置,而这个纹理状态与纹理对象捆绑,那它也是纹理对象的一部
分。这个函数是我们自定义的函数。当设置Mip贴图的过滤方式时会生成Mip贴图 glGenerateMipmap(GL_TEXTURE_2D)
在顶部声明变量textureID,即GLuint textureID;
在程序结束时调用了ShutdownRC函数进行glDeleteTextures(1, &textureID); 删除纹理对象
讲解MakePyramid函数,它是构建了一个金字塔。
//构建金字塔底面的其中一个三角面,(左下角,右下角,右上角)构成
pyramidBatch.Normal3f(0.0f, -1.0f, 0.0f);
pyramidBatch.MultiTexCoord2f(0, 0.0f, 0.0f); // 第一个参数是0,代表纹理层次(存储着色器都设置为0即可 后续第七章会讲解 多重纹理时应用),后2个参数是纹理坐标。
pyramidBatch.Vertex3f(-1.0f, -1.0f, -1.0f);
pyramidBatch.Normal3f(0.0f, -1.0f, 0.0f);
pyramidBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
pyramidBatch.Vertex3f(1.0f, -1.0f, -1.0f);
pyramidBatch.Normal3f(0.0f, -1.0f, 0.0f);
pyramidBatch.MultiTexCoord2f(0, 1.0f, 1.0f);
pyramidBatch.Vertex3f(1.0f, -1.0f, 1.0f);
下面这部分内容是利用了m3dFindNormal函数 传入第二、第三、第四参数,根据这些顶点位置找到这3个顶点构成的面的法线返回给n。然后继续用pyramidBatch进行设置顶点数据(法线、纹理坐标、顶点坐标)
M3DVector3f vApex = { 0.0f, 1.0f, 0.0f };
M3DVector3f vFrontLeft = { -1.0f, -1.0f, 1.0f };
M3DVector3f vFrontRight = { 1.0f, -1.0f, 1.0f };
M3DVector3f vBackLeft = { -1.0f, -1.0f, -1.0f };
M3DVector3f vBackRight = { 1.0f, -1.0f, -1.0f };
M3DVector3f n;
//如下代码是构建金字塔Z轴为1的正斜面(其中2个顶点Z轴为1) 其他三个斜面以此类推进行(注意是顺时针设置的顶点数据!)
m3dFindNormal(n, vApex, vFrontLeft, vFrontRight);
pyramidBatch.Normal3fv(n);
pyramidBatch.MultiTexCoord2f(0, 0.5f, 1.0f);
pyramidBatch.Vertex3fv(vApex); // Apex
pyramidBatch.Normal3fv(n);
pyramidBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
pyramidBatch.Vertex3fv(vFrontLeft); // Front left corner
pyramidBatch.Normal3fv(n);
pyramidBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
pyramidBatch.Vertex3fv(vFrontRight); // Front right corner
等构建完pyramidBatch批次后,再用着色器渲染之前要再一次进行 glBindTexture(GL_TEXTURE_2D, textureID); 捆绑纹理对象。(书上说本例也可以不进行第二次绑定了,因为已经绑定过了,但最好还是保证在batch.Draw之前进行绑定一次需要渲染时用到的纹理对象(例如,在Draw之前有人进行了对这个绑定换成了其他的纹理对象,那么渲染时就可能用了另一个纹理对象的纹理状态中的纹理贴图进行渲染了)
shaderManager.UseStockShader(GLT_SHADER_TEXTURE_POINT_LIGHT_DIFF,
transformPipeline.GetModelViewMatrix(),
transformPipeline.GetProjectionMatrix(),
vLightPos, vWhite, 0);
// Pyramid.cpp
// OpenGL SuperBible, Chapter 5
// Demonstrates Texture mapping a pyramid
// 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 <GLBatch.h>
#include <GLGeometryTransform.h>
#include <math.h>
#ifdef __APPLE__
#include <glut/glut.h>
#else
#define FREEGLUT_STATIC
#include <GL/glut.h>
#endif
/
// An assortment of needed classes
GLShaderManager shaderManager;
GLMatrixStack modelViewMatrix;
GLMatrixStack projectionMatrix;
GLFrame cameraFrame;
GLFrame objectFrame;
GLFrustum viewFrustum;
GLBatch pyramidBatch;
GLuint textureID;
GLGeometryTransform transformPipeline;
M3DMatrix44f shadowMatrix;
void MakePyramid(GLBatch& pyramidBatch)
{
pyramidBatch.Begin(GL_TRIANGLES, 18, 1);
// Bottom of pyramid
pyramidBatch.Normal3f(0.0f, -1.0f, 0.0f);
pyramidBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
pyramidBatch.Vertex3f(-1.0f, -1.0f, -1.0f);
pyramidBatch.Normal3f(0.0f, -1.0f, 0.0f);
pyramidBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
pyramidBatch.Vertex3f(1.0f, -1.0f, -1.0f);
pyramidBatch.Normal3f(0.0f, -1.0f, 0.0f);
pyramidBatch.MultiTexCoord2f(0, 1.0f, 1.0f);
pyramidBatch.Vertex3f(1.0f, -1.0f, 1.0f);
pyramidBatch.Normal3f(0.0f, -1.0f, 0.0f);
pyramidBatch.MultiTexCoord2f(0, 0.0f, 1.0f);
pyramidBatch.Vertex3f(-1.0f, -1.0f, 1.0f);
pyramidBatch.Normal3f(0.0f, -1.0f, 0.0f);
pyramidBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
pyramidBatch.Vertex3f(-1.0f, -1.0f, -1.0f);
pyramidBatch.Normal3f(0.0f, -1.0f, 0.0f);
pyramidBatch.MultiTexCoord2f(0, 1.0f, 1.0f);
pyramidBatch.Vertex3f(1.0f, -1.0f, 1.0f);
M3DVector3f vApex = { 0.0f, 1.0f, 0.0f };
M3DVector3f vFrontLeft = { -1.0f, -1.0f, 1.0f };
M3DVector3f vFrontRight = { 1.0f, -1.0f, 1.0f };
M3DVector3f vBackLeft = { -1.0f, -1.0f, -1.0f };
M3DVector3f vBackRight = { 1.0f, -1.0f, -1.0f };
M3DVector3f n;
// Front of Pyramid
m3dFindNormal(n, vApex, vFrontLeft, vFrontRight);
pyramidBatch.Normal3fv(n);
pyramidBatch.MultiTexCoord2f(0, 0.5f, 1.0f);
pyramidBatch.Vertex3fv(vApex); // Apex
pyramidBatch.Normal3fv(n);
pyramidBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
pyramidBatch.Vertex3fv(vFrontLeft); // Front left corner
pyramidBatch.Normal3fv(n);
pyramidBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
pyramidBatch.Vertex3fv(vFrontRight); // Front right corner
m3dFindNormal(n, vApex, vBackLeft, vFrontLeft);
pyramidBatch.Normal3fv(n);
pyramidBatch.MultiTexCoord2f(0, 0.5f, 1.0f);
pyramidBatch.Vertex3fv(vApex); // Apex
pyramidBatch.Normal3fv(n);
pyramidBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
pyramidBatch.Vertex3fv(vBackLeft); // Back left corner
pyramidBatch.Normal3fv(n);
pyramidBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
pyramidBatch.Vertex3fv(vFrontLeft); // Front left corner
m3dFindNormal(n, vApex, vFrontRight, vBackRight);
pyramidBatch.Normal3fv(n);
pyramidBatch.MultiTexCoord2f(0, 0.5f, 1.0f);
pyramidBatch.Vertex3fv(vApex); // Apex
pyramidBatch.Normal3fv(n);
pyramidBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
pyramidBatch.Vertex3fv(vFrontRight); // Front right corner
pyramidBatch.Normal3fv(n);
pyramidBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
pyramidBatch.Vertex3fv(vBackRight); // Back right cornder
m3dFindNormal(n, vApex, vBackRight, vBackLeft);
pyramidBatch.Normal3fv(n);
pyramidBatch.MultiTexCoord2f(0, 0.5f, 1.0f);
pyramidBatch.Vertex3fv(vApex); // Apex
pyramidBatch.Normal3fv(n);
pyramidBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
pyramidBatch.Vertex3fv(vBackRight); // Back right cornder
pyramidBatch.Normal3fv(n);
pyramidBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
pyramidBatch.Vertex3fv(vBackLeft); // Back left corner
pyramidBatch.End();
}
// Load a TGA as a 2D Texture. Completely initialize the state
bool LoadTGATexture(const char *szFileName, GLenum minFilter, GLenum magFilter, GLenum wrapMode)
{
GLbyte *pBits;
int nWidth, nHeight, nComponents;
GLenum eFormat;
// Read the texture bits
pBits = gltReadTGABits(szFileName, &nWidth, &nHeight, &nComponents, &eFormat);
if (pBits == NULL)
return false;
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, wrapMode);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, wrapMode);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, minFilter);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, magFilter);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexImage2D(GL_TEXTURE_2D, 0, nComponents, nWidth, nHeight, 0,
eFormat, GL_UNSIGNED_BYTE, pBits);
free(pBits);
if (minFilter == GL_LINEAR_MIPMAP_LINEAR ||
minFilter == GL_LINEAR_MIPMAP_NEAREST ||
minFilter == GL_NEAREST_MIPMAP_LINEAR ||
minFilter == GL_NEAREST_MIPMAP_NEAREST)
glGenerateMipmap(GL_TEXTURE_2D);
return true;
}
///
// This function does any needed initialization on the rendering context.
// This is the first opportunity to do any OpenGL related tasks.
void SetupRC()
{
// Black background
glClearColor(0.7f, 0.7f, 0.7f, 1.0f);
shaderManager.InitializeStockShaders();
glEnable(GL_DEPTH_TEST);
glGenTextures(1, &textureID);
glBindTexture(GL_TEXTURE_2D, textureID);
LoadTGATexture("stone.tga", GL_LINEAR, GL_LINEAR, GL_CLAMP_TO_EDGE);
MakePyramid(pyramidBatch);
cameraFrame.MoveForward(-7.0f);
}
///
// Cleanup... such as deleting texture objects
void ShutdownRC(void)
{
glDeleteTextures(1, &textureID);
}
///
// Called to draw scene
void RenderScene(void)
{
static GLfloat vLightPos[] = { 1.0f, 1.0f, 0.0f };
static GLfloat vWhite[] = { 1.0f, 1.0f, 1.0f, 1.0f };
// Clear the window with current clearing color
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
modelViewMatrix.PushMatrix();
M3DMatrix44f mCamera;
cameraFrame.GetCameraMatrix(mCamera);
modelViewMatrix.MultMatrix(mCamera);
M3DMatrix44f mObjectFrame;
objectFrame.GetMatrix(mObjectFrame);
modelViewMatrix.MultMatrix(mObjectFrame);
glBindTexture(GL_TEXTURE_2D, textureID);
shaderManager.UseStockShader(GLT_SHADER_TEXTURE_POINT_LIGHT_DIFF,
transformPipeline.GetModelViewMatrix(),
transformPipeline.GetProjectionMatrix(),
vLightPos, vWhite, 0);
pyramidBatch.Draw();
modelViewMatrix.PopMatrix();
// Flush drawing commands
glutSwapBuffers();
}
// Respond to arrow keys by moving the camera frame of reference
void SpecialKeys(int key, int x, int y)
{
if (key == GLUT_KEY_UP)
objectFrame.RotateWorld(m3dDegToRad(-5.0f), 1.0f, 0.0f, 0.0f);
if (key == GLUT_KEY_DOWN)
objectFrame.RotateWorld(m3dDegToRad(5.0f), 1.0f, 0.0f, 0.0f);
if (key == GLUT_KEY_LEFT)
objectFrame.RotateWorld(m3dDegToRad(-5.0f), 0.0f, 1.0f, 0.0f);
if (key == GLUT_KEY_RIGHT)
objectFrame.RotateWorld(m3dDegToRad(5.0f), 0.0f, 1.0f, 0.0f);
glutPostRedisplay();
}
///
// Window has changed size, or has just been created. In either case, we need
// to use the window dimensions to set the viewport and the projection matrix.
void ChangeSize(int w, int h)
{
glViewport(0, 0, w, h);
viewFrustum.SetPerspective(35.0f, float(w) / float(h), 1.0f, 500.0f);
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("Pyramid");
glutReshapeFunc(ChangeSize);
glutSpecialFunc(SpecialKeys);
glutDisplayFunc(RenderScene);
GLenum err = glewInit();
if (GLEW_OK != err) {
fprintf(stderr, "GLEW Error: %s\n", glewGetErrorString(err));
return 1;
}
SetupRC();
glutMainLoop();
ShutdownRC();
return 0;
}