【OpenGL】各向异性过滤案例

第一张图是GL_NEAREST没开启各向异性的，第二张图开启了各向异性变的比较不那么斑驳了，其他效果可自行测试。

// Tunnel.cpp
// Demonstrates mipmapping and using texture objects
// OpenGL SuperBible
// Richard S. Wright Jr.
#pragma comment(lib,"gltools.lib")
#include <GLTools.h>
#include <GLShaderManager.h>
#include <GLFrustum.h>
#include <GLBatch.h>
#include <GLFrame.h>
#include <GLMatrixStack.h>
#include <GLGeometryTransform.h>#ifdef __APPLE__
#include <glut/glut.h>
#else
#define FREEGLUT_STATIC
#include <GL/glut.h>
#endifGLShaderManager       shaderManager;          // Shader Manager
GLMatrixStack       modelViewMatrix;        // Modelview Matrix
GLMatrixStack       projectionMatrix;       // Projection Matrix
GLFrustum           viewFrustum;            // View Frustum
GLGeometryTransform transformPipeline;      // Geometry Transform PipelineGLBatch             floorBatch;
GLBatch             ceilingBatch;
GLBatch             leftWallBatch;
GLBatch             rightWallBatch;GLfloat             viewZ = -65.0f;// Texture objects
#define TEXTURE_BRICK   0
#define TEXTURE_FLOOR   1
#define TEXTURE_CEILING 2
#define TEXTURE_COUNT   3
GLuint  textures[TEXTURE_COUNT];
const char *szTextureFiles[TEXTURE_COUNT] = { "brick.tga", "floor.tga", "ceiling.tga" };///
// Change texture filter for each texture object
void ProcessMenu(int value)
{GLfloat fLargest;GLint iLoop;for (iLoop = 0; iLoop < TEXTURE_COUNT; iLoop++){glBindTexture(GL_TEXTURE_2D, textures[iLoop]);switch (value){case 0:glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);break;case 1:glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);break;case 2:glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST_MIPMAP_NEAREST);break;case 3:glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST_MIPMAP_LINEAR);break;case 4:glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);break;case 5:glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);break;case 6:glGetFloatv(GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT, &fLargest);glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT, fLargest);break;case 7:glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT, 1.0f);break;}}// Trigger RedrawglutPostRedisplay();
}//
// This function does any needed initialization on the rendering
// context.  Here it sets up and initializes the texture objects.
void SetupRC()
{GLbyte *pBytes;GLint iWidth, iHeight, iComponents;GLenum eFormat;GLint iLoop;// Black backgroundglClearColor(0.0f, 0.0f, 0.0f, 1.0f);shaderManager.InitializeStockShaders();// Load texturesglGenTextures(TEXTURE_COUNT, textures);for (iLoop = 0; iLoop < TEXTURE_COUNT; iLoop++){// Bind to next texture objectglBindTexture(GL_TEXTURE_2D, textures[iLoop]);// Load texture, set filter and wrap modespBytes = gltReadTGABits(szTextureFiles[iLoop], &iWidth, &iHeight,&iComponents, &eFormat);// Load texture, set filter and wrap modesglTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);glTexImage2D(GL_TEXTURE_2D, 0, iComponents, iWidth, iHeight, 0, eFormat, GL_UNSIGNED_BYTE, pBytes);glGenerateMipmap(GL_TEXTURE_2D);// Don't need original texture data any morefree(pBytes);}// Build GeometryGLfloat z;floorBatch.Begin(GL_TRIANGLE_STRIP, 28, 1);for (z = 60.0f; z >= 0.0f; z -= 10.0f){floorBatch.MultiTexCoord2f(0, 0.0f, 0.0f);floorBatch.Vertex3f(-10.0f, -10.0f, z);floorBatch.MultiTexCoord2f(0, 1.0f, 0.0f);floorBatch.Vertex3f(10.0f, -10.0f, z);floorBatch.MultiTexCoord2f(0, 0.0f, 1.0f);floorBatch.Vertex3f(-10.0f, -10.0f, z - 10.0f);floorBatch.MultiTexCoord2f(0, 1.0f, 1.0f);floorBatch.Vertex3f(10.0f, -10.0f, z - 10.0f);}floorBatch.End();ceilingBatch.Begin(GL_TRIANGLE_STRIP, 28, 1);for (z = 60.0f; z >= 0.0f; z -= 10.0f){ceilingBatch.MultiTexCoord2f(0, 0.0f, 1.0f);ceilingBatch.Vertex3f(-10.0f, 10.0f, z - 10.0f);ceilingBatch.MultiTexCoord2f(0, 1.0f, 1.0f);ceilingBatch.Vertex3f(10.0f, 10.0f, z - 10.0f);ceilingBatch.MultiTexCoord2f(0, 0.0f, 0.0f);ceilingBatch.Vertex3f(-10.0f, 10.0f, z);ceilingBatch.MultiTexCoord2f(0, 1.0f, 0.0f);ceilingBatch.Vertex3f(10.0f, 10.0f, z);}ceilingBatch.End();leftWallBatch.Begin(GL_TRIANGLE_STRIP, 28, 1);for (z = 60.0f; z >= 0.0f; z -= 10.0f){leftWallBatch.MultiTexCoord2f(0, 0.0f, 0.0f);leftWallBatch.Vertex3f(-10.0f, -10.0f, z);leftWallBatch.MultiTexCoord2f(0, 0.0f, 1.0f);leftWallBatch.Vertex3f(-10.0f, 10.0f, z);leftWallBatch.MultiTexCoord2f(0, 1.0f, 0.0f);leftWallBatch.Vertex3f(-10.0f, -10.0f, z - 10.0f);leftWallBatch.MultiTexCoord2f(0, 1.0f, 1.0f);leftWallBatch.Vertex3f(-10.0f, 10.0f, z - 10.0f);}leftWallBatch.End();rightWallBatch.Begin(GL_TRIANGLE_STRIP, 28, 1);for (z = 60.0f; z >= 0.0f; z -= 10.0f){rightWallBatch.MultiTexCoord2f(0, 0.0f, 0.0f);rightWallBatch.Vertex3f(10.0f, -10.0f, z);rightWallBatch.MultiTexCoord2f(0, 0.0f, 1.0f);rightWallBatch.Vertex3f(10.0f, 10.0f, z);rightWallBatch.MultiTexCoord2f(0, 1.0f, 0.0f);rightWallBatch.Vertex3f(10.0f, -10.0f, z - 10.0f);rightWallBatch.MultiTexCoord2f(0, 1.0f, 1.0f);rightWallBatch.Vertex3f(10.0f, 10.0f, z - 10.0f);}rightWallBatch.End();
}///
// Shutdown the rendering context. Just deletes the
// texture objects
void ShutdownRC(void)
{glDeleteTextures(TEXTURE_COUNT, textures);
}///
// Respond to arrow keys, move the viewpoint back
// and forth
void SpecialKeys(int key, int x, int y)
{if (key == GLUT_KEY_UP)viewZ += 0.5f;if (key == GLUT_KEY_DOWN)viewZ -= 0.5f;// Refresh the WindowglutPostRedisplay();
}/
// Change viewing volume and viewport.  Called when window is resized
void ChangeSize(int w, int h)
{GLfloat fAspect;// Prevent a divide by zeroif (h == 0)h = 1;// Set Viewport to window dimensionsglViewport(0, 0, w, h);fAspect = (GLfloat)w / (GLfloat)h;// Produce the perspective projectionviewFrustum.SetPerspective(80.0f, fAspect, 1.0, 120.0);projectionMatrix.LoadMatrix(viewFrustum.GetProjectionMatrix());transformPipeline.SetMatrixStacks(modelViewMatrix, projectionMatrix);}///
// Called to draw scene
void RenderScene(void)
{// Clear the window with current clearing colorglClear(GL_COLOR_BUFFER_BIT);modelViewMatrix.PushMatrix();modelViewMatrix.Translate(0.0f, 0.0f, viewZ);shaderManager.UseStockShader(GLT_SHADER_TEXTURE_REPLACE, transformPipeline.GetModelViewProjectionMatrix(), 0);glBindTexture(GL_TEXTURE_2D, textures[TEXTURE_FLOOR]);floorBatch.Draw();glBindTexture(GL_TEXTURE_2D, textures[TEXTURE_CEILING]);ceilingBatch.Draw();glBindTexture(GL_TEXTURE_2D, textures[TEXTURE_BRICK]);leftWallBatch.Draw();rightWallBatch.Draw();modelViewMatrix.PopMatrix();// Buffer swapglutSwapBuffers();
}//
// Program entry point
int main(int argc, char *argv[])
{gltSetWorkingDirectory(argv[0]);// Standard initialization stuffglutInit(&argc, argv);glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);glutInitWindowSize(800, 600);glutCreateWindow("Anisotropic Tunnel");glutReshapeFunc(ChangeSize);glutSpecialFunc(SpecialKeys);glutDisplayFunc(RenderScene);// Add menu entries to change filterglutCreateMenu(ProcessMenu);glutAddMenuEntry("GL_NEAREST", 0);glutAddMenuEntry("GL_LINEAR", 1);glutAddMenuEntry("GL_NEAREST_MIPMAP_NEAREST", 2);glutAddMenuEntry("GL_NEAREST_MIPMAP_LINEAR", 3);glutAddMenuEntry("GL_LINEAR_MIPMAP_NEAREST", 4);glutAddMenuEntry("GL_LINEAR_MIPMAP_LINEAR", 5);glutAddMenuEntry("Anisotropic Filter", 6);glutAddMenuEntry("Anisotropic Off", 7);glutAttachMenu(GLUT_RIGHT_BUTTON);GLenum err = glewInit();if (GLEW_OK != err) {fprintf(stderr, "GLEW Error: %s\n", glewGetErrorString(err));return 1;}// Startup, loop, shutdownSetupRC();glutMainLoop();ShutdownRC();return 0;
}

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