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yan_qingsong

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About yan_qingsong

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  1. In OpenGL,is there a build-in function that can get the quantity of drawn triangles or points?
  2. yan_qingsong

    why the gl_ClipDistance[] doesn't work?

    @samoth You are right. When I compile the vertexshader using the reference compiler,it emit a warning. The warning says that version 410 is not yet complete. how to solve this problem?
  3. yan_qingsong

    why the gl_ClipDistance[] doesn't work?

    The problem is solved.The code is right. GPU is the key. When I change the AMD card to NVIDIA card, the code works well.
  4. yan_qingsong

    why the gl_ClipDistance[] doesn't work?

    actually,I had read related content in OpenGL SuperBible 5th Ed,OpenGL SuperBible 6th Ed and OpenGL Shading Language 3rd Ed. And I set “glEnable(GL_CLIP_DISTANCE0)” in the application of course.
  5. yan_qingsong

    why the gl_ClipDistance[] doesn't work?

        I set "gl_ClipDistance[0] = -1.0;" as you saied, but what make me confused is that the result is not changed, my model didn't disappear.
  6. yan_qingsong

    why the gl_ClipDistance[] doesn't work?

        Thank you! I tried "glEnable(GL_CLIP_DISTANCE0) ;glEnable(GL_CLIP_DISTANCE1) ;",but it still didn't work. I guess maybe something else is not right.
  7. I just can't understand why the gl_ClipDistance doesn't work. The result is the same as I didn't set the gl_ClipDistance. I had set glEnable(GL_CLIP_DISTANCE0+2) by application. the vertex shader is like this: #version 410 uniform mat4 mvpMatrix; //.......some other uniforms here in vec2 vVertex; uniform vec4 clip_plane=vec4(1.0,1.0,0.0,0.85); uniform vec4 clip_sphere=vec4(0.0,0.0,0.0,10.0); void main(void) { //........some other code,include vec2 worldPos vec4 worldPosition=vec4(worldPos.x,height,worldPos.y,1.0); gl_ClipDistance[0]=dot(worldPosition,clip_plane); gl_ClipDistance[1]=length(worldPosition.xyz/worldPosition.w-clip_sphere.xyz)-clip_sphere.w; gl_Position = mvpMatrix * position; }
  8. I'm a new learner about OpenGL and GLSL. I'm coding a program in which i wanna store a group of datas in a texture and get the data by sampling the texture in vertex shader. Then i want to set the datas as the y coodinates of terrain positions. But i get a trouble that it's failed and i can't get a correct value___all the y coodinates are 0.   The main code is below:       GLuint  terrainShader;      // The perspective demonstration shader     GLint   locMVP,locTex;                 // The location of the uniform in vertex shader          GLuint  vao;                    // The VAO     GLuint  vertexBuffer;               GLuint elementBuffer;     GLuint vertexTexture;         const int n=127;     float verteces[n*n*2];// vertex array     GLuint vIndexFine[(n-1)*2*n];//index array     GLsizei countFine[n-1];     GLvoid* offsetFine[n-1];          float *data=new float[n*n];     terrainShader = gltLoadShaderPairWithAttributes("terrain.vp", "terrain.fp", 1,                                 GLT_ATTRIBUTE_VERTEX, "vVertex");              locMVP = glGetUniformLocation(terrainShader, "mvpMatrix");     locTex = glGetUniformLocation(terrainShader, "vertexTexture");          //creat a terrain with size of n*n     for(int i=0;i<n;i++)     {     int sum=i*n;     for(int j=0;j<n;j++)     {     verteces[(sum+j)*2]=float(j);     verteces[(sum+j)*2+1]=float(i);     }     }     //initialize the index array     for(int i=0;i<n-1;i++)     {     if(i==0) //the first line     {     for(int j=0;j<n;j++)     {     vIndexFine[2*j]=j;     vIndexFine[2*j+1]=j+n;     }     }     else     { //if it's not the first line,then just add n to get the indexes of new line     for(int k=0;k<2*n;k++)     {     vIndexFine[i*2*n+k]=vIndexFine[(i-1)*2*n+k]+n;     }     }     }              glGenVertexArrays(1, &vao);         glBindVertexArray(vao);              glGenBuffers(1, &vertexBuffer);         glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);         glBufferData(GL_ARRAY_BUFFER, sizeof(verteces), verteces, GL_STATIC_DRAW);         glVertexAttribPointer(GLT_ATTRIBUTE_VERTEX, 2, GL_FLOAT, GL_FALSE, 0, NULL);         glEnableVertexAttribArray(GLT_ATTRIBUTE_VERTEX);          glGenBuffers(1, &elementBuffer);     glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementBuffer);     glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(vIndexFine), vIndexFine, GL_STATIC_DRAW);             //initialize data array with random integers between 1 and 100     for(int i=0;i<n*n;i++)     data[i]=float(rand()%100)/100.0;                  //creat a texture and store data     glGenTextures(1, &vertexTexture);     glActiveTexture(GL_TEXTURE0);     glBindTexture(GL_TEXTURE_2D, vertexTexture);     glTexImage2D(GL_TEXTURE_2D, 0, GL_R32F, n,n, 0,GL_RED, GL_FLOAT, data);          //compute every trianglestrip's indexcount and offset     int temp=n*2*sizeof(GLuint);     for(int i=0;i<n-1;i++)     {     offsetFine[i]=(void*)(temp*i);     countFine[i]=GLsizei(n*2);     }          glUseProgram(terrainShader);     glUniform1i(locTex, 0);          modelViewMatrix.PushMatrix(viewFrame);     modelViewMatrix.Translate(-n/2.0, -10.0f, -n/2.0);     glUniformMatrix4fv(locMVP, 1, GL_FALSE, transformPipeline.GetModelViewProjectionMatrix());     glMultiDrawElements(GL_TRIANGLE_STRIP,countFine,GL_UNSIGNED_INT, (const GLvoid**)offsetFine,n-1);     modelViewMatrix.PopMatrix();   the vertex shader:       #version 410          uniform mat4 mvpMatrix;     uniform sampler2D vertexTexture;     in vec2 vVertex;          void main(void)          {          vec2 vTexCoords=vVertex/127.0;         float height = texture2DLod(vertexTexture, vTexCoords,0.0).x*100.0;         vec4 position=vec4(vVertex.x,height,vVertex.y,1.0);         gl_Position = mvpMatrix * position;         } i think  the mistake must be the part of storing datas in application or the part of fetching datas from  the texture in vertex shader. can sombody point it out for me? 
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