Cg之重影效果范例

这一节主要讲了三点内容：

1. out类型限定符的作用。该限定词限定的形式参数被称为call-by-result参数。也就是说，Cg必须把由out限定的形式参数的最终值传递给它对应的调用参数。
2. 顶点程序中如何实现对纹理坐标的偏移。
3. 片断程序中如何实现对两个纹理的混合。

附上经自己整理后的源代码：

1. //顶点程序:twoTextures_vertex.cg
2. void main(float2 position : POSITION,
3.           float2 texCoord : TEXCOORD0,
4.           
5.           out float4 oPosition : POSITION,
6.           out float2 leftTexCoord : TEXCOORD0,
7.           out float2 rightTexCoord : TEXCOORD1,
8.           
9.           uniform float2 leftSeparation,
10.           uniform float2 rightSeparation)
11. {
12.      oPosition = float4(position,0,1);
13.      leftTexCoord = texCoord + leftSeparation;
14.      rightTexCoord = texCoord + rightSeparation; 
15. }

 

1. //片断程序：twoTextures_fragment.cg
2. void main(float2 leftTexCoord : TEXCOORD0,
3.           float2 rightTexCoord : TEXCOORD1,
4.           
5.           out float4 color : COLOR,
6.           uniform sampler2D decal)
7. {
8.     float4 leftColor = tex2D(decal,leftTexCoord);
9.     float4 rightColor = tex2D(decal,rightTexCoord);
10.     color = lerp(leftColor,rightColor,0.5);
11. }

 

1. //整理后的应用程序 2008-9-9 13:24:48
2. #ifdef _MSC_VER
3. #pragma comment( lib, "cg.lib" )
4. #pragma comment( lib, "cgGL.lib" )
5. #endif
8. #include <stdio.h>    /* for printf and NULL */
9. #include <stdlib.h>   /* for exit */
10. #if __APPLE__
11. #include <GLUT/glut.h>
12. #else
13. #include <GL/glut.h>
14. #endif
15. #include <Cg/cg.h>    /* Can't include this?  Is Cg Toolkit installed! */
16. #include <Cg/cgGL.h>
18. static const char *myProgramName = "twoTextures";
19. static CGcontext   myCgContext;//Cg上下文环境
21. static CGprofile   myCgVertexProfile;//顶点profile
22. static CGprogram   myCgVertexProgram;//顶点程序
23. static CGparameter myCgVertexParam_leftSeparation;//顶点程序参数
24. static CGparameter myCgVertexParam_rightSeparation;//顶点程序参数
25. static const char  *myVertexProgramFileName = "twoTextures_vertex.cg",//顶点Cg源文件
26.                    *myVertexProgramName = "main";//顶点程序入口函数
28. static CGprofile   myCgFragmentProfile;//片断profile
29. static CGprogram   myCgFragmentProgram;//片断程序
30. static CGparameter myCgFragmentParam_decal;//片断程序参数
31. static const char  *myFragmentProgramFileName = "twoTextures_fragment.cg",//片断Cg源文件
32.                    *myFragmentProgramName = "main";//片断程序入口函数
34. static const GLubyte  //纹理图像数据
35. myDemonTextureImage[3*(128*128)] = {
36. /* RGB8 image data for a mipmapped 128x128 demon texture */
37. #include "demon_image.h"
38. };
40. static void checkForCgError(const char *situation)
41. {
42.   CGerror error;
43.   const char *string = cgGetLastErrorString(&error);
45.   if (error != CG_NO_ERROR) {
46.     printf("%s: %s: %s/n",
47.       myProgramName, situation, string);
48.     if (error == CG_COMPILER_ERROR) {
49.       printf("%s/n", cgGetLastListing(myCgContext));
50.     }
51.     exit(1);
52.   }
53. }
55. /* Forward declared GLUT callbacks registered by main. */
56. static void display(void);
57. static void keyboard(unsigned char c, int x, int y);
59. static void initTexture(void);
60. static void initCg(void);
61. static void initCgVertexProgram(void);
62. static void initCgFragmentProgram(void);
64. int main(int argc, char **argv)
65. {
66.       glutInitWindowSize(400, 400);
67.     glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
68.     glutInit(&argc, argv);
70.     glutCreateWindow(myProgramName);
71.     glutDisplayFunc(display);
72.     glutKeyboardFunc(keyboard);
74.     glClearColor(0.1, 0.3, 0.6, 0.0);  /* Blue background */
75.     initTexture();
76.   initCg();
77.   glutMainLoop();
78.   return 0;
79. }
82.     static void initTexture(void){
83.           glPixelStorei(GL_UNPACK_ALIGNMENT, 1); /*Tightly packed texture data.*/
84.       glBindTexture(GL_TEXTURE_2D, 666);
85.       /* Load demon decal texture with mipmaps. */
86.             gluBuild2DMipmaps(GL_TEXTURE_2D, GL_RGB8,
87.             128, 128, GL_RGB, GL_UNSIGNED_BYTE, myDemonTextureImage);
88.             glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
89.             GL_LINEAR_MIPMAP_LINEAR);
90.     }
91.     
92.     static void initCg(void){
93.           myCgContext = cgCreateContext();//得到当前上下文环境
94.           checkForCgError("creating context");
95.           cgGLSetDebugMode( CG_FALSE );
96.           cgSetParameterSettingMode(myCgContext, CG_DEFERRED_PARAMETER_SETTING);
97.           
98.           initCgVertexProgram();
99.           initCgFragmentProgram();
100. }
102. static void initCgVertexProgram(void){
103.           //-----------------------------选择顶点和片断的profile---------------------------------
104.           myCgVertexProfile = cgGLGetLatestProfile(CG_GL_VERTEX);
105.           cgGLSetOptimalOptions(myCgVertexProfile);
106.           checkForCgError("selecting vertex profile");
107.           //-----------------------------选择顶点和片断的profile-----------------------------
108.           
109.           //-----------------------------载入顶点程序和参数-----------------------------
110.           myCgVertexProgram =
111.             cgCreateProgramFromFile(
112.               myCgContext,              /* Cg runtime context */
113.               CG_SOURCE,                /* Program in human-readable form */
114.               myVertexProgramFileName,  /* Name of file containing program */
115.               myCgVertexProfile,        /* Profile: OpenGL ARB vertex program */
116.               myVertexProgramName,      /* Entry function name */
117.               NULL);                    /* No extra compiler options */
118.           checkForCgError("creating vertex program from file");
119.           cgGLLoadProgram(myCgVertexProgram);
120.           checkForCgError("loading vertex program");
121.           
122.           myCgVertexParam_leftSeparation =
123.             cgGetNamedParameter(myCgVertexProgram, "leftSeparation");
124.           myCgVertexParam_rightSeparation =
125.             cgGetNamedParameter(myCgVertexProgram, "rightSeparation");
126.           cgSetParameter2f(myCgVertexParam_leftSeparation,  -0.3, 0);
127.           cgSetParameter2f(myCgVertexParam_rightSeparation, 0.3, 0);
128.      //-----------------------------载入顶点程序和参数-----------------------------  
129.     }
130.     
131.     static void initCgFragmentProgram(void){
132.           myCgFragmentProfile = cgGLGetLatestProfile(CG_GL_FRAGMENT);
133.           cgGLSetOptimalOptions(myCgFragmentProfile);
134.           checkForCgError("selecting fragment profile");
135.         
136.           myCgFragmentProgram =
137.             cgCreateProgramFromFile(
138.               myCgContext,                /* Cg runtime context */
139.               CG_SOURCE,                  /* Program in human-readable form */
140.               myFragmentProgramFileName,  /* Name of file containing program */
141.               myCgFragmentProfile,        /* Profile: OpenGL ARB vertex program */
142.               myFragmentProgramName,      /* Entry function name */
143.               NULL);        
144.           checkForCgError("creating fragment program from file");
145.         
146.           cgGLLoadProgram(myCgFragmentProgram);
147.           checkForCgError("loading fragment program");
148.         
149.           myCgFragmentParam_decal =
150.             cgGetNamedParameter(myCgFragmentProgram, "decal");
151.           checkForCgError("getting decal parameter");   
152.           cgGLSetTextureParameter(myCgFragmentParam_decal, 666);    
153.           checkForCgError("setting decal 2D texture");      
154.     }
156. static void display(void)
157. {
158.   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
159.   
160.   cgGLBindProgram(myCgVertexProgram);
161.   checkForCgError("binding vertex program");
163.   cgGLEnableProfile(myCgVertexProfile);
164.   checkForCgError("enabling vertex profile");  
166.   cgGLBindProgram(myCgFragmentProgram);
167.   checkForCgError("binding Fragment program");
169.   cgGLEnableProfile(myCgFragmentProfile);
170.   checkForCgError("enabling Fragment profile");
172.   glBegin(GL_TRIANGLES);
173.     glTexCoord2f(0, 0);
174.     glVertex2f(-0.8, 0.8);
176.     glTexCoord2f(1, 0);
177.     glVertex2f(0.8, 0.8);
179.     glTexCoord2f(0.5, 1);
180.     glVertex2f(0.0, -0.8);
181.   glEnd();
183.   cgGLDisableProfile(myCgVertexProfile);
184.   cgGLDisableProfile(myCgFragmentProfile);
185.   checkForCgError("disabling vertex profile");
187.   glutSwapBuffers();
188. }
190. static void keyboard(unsigned char c, int x, int y)
191. {
192.   switch (c) {
193.   case 27:  /* Esc key */
194.     /* Demonstrate proper deallocation of Cg runtime data structures.
195.        Not strictly necessary if we are simply going to exit. */
196.     cgDestroyProgram(myCgVertexProgram);
197.     cgDestroyContext(myCgContext);
198.     exit(0);
199.     break;
200.   }
201. }