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When I pass non max values into texture buffer, while rendering it draws geometry with colors at max values. I found this issue while using glTexBuffer() API.

E.g. Let’s assume my texture data is GLubyte, when I pass any value less than 255, then the color is same as that of drawn with 255, instead of mixture of black and that color.
I tried on AMD and nvidia card, but the results are same. Can you tell me where could be going wrong?

I am copying my code here:

Vert shader:

in vec2 a_position;
uniform float offset_x;
void main()
{ 
   gl_Position = vec4(a_position.x + offset_x, a_position.y, 1.0, 1.0);
}

Frag shader:

out vec4 Color;
uniform isamplerBuffer sampler;
uniform int index;
void main() 
{
   Color=texelFetch(sampler,index);

}

Code:

GLubyte arr[]={128,5,250};
glGenBuffers(1,&bufferid);

glBindBuffer(GL_TEXTURE_BUFFER,bufferid);

glBufferData(GL_TEXTURE_BUFFER,sizeof(arr),arr,GL_STATIC_DRAW);
glBindBuffer(GL_TEXTURE_BUFFER,0);

glGenTextures(1, &buffer_texture);   

glBindTexture(GL_TEXTURE_BUFFER, buffer_texture);
glTexBuffer(GL_TEXTURE_BUFFER, GL_R8, bufferid);


glUniform1f(glGetUniformLocation(shader_data.psId,"offset_x"),0.0f);
glUniform1i(glGetUniformLocation(shader_data.psId,"sampler"),0);
glUniform1i(glGetUniformLocation(shader_data.psId,"index"),0);

glGenBuffers(1,&bufferid1);

glBindBuffer(GL_ARRAY_BUFFER,bufferid1);
glBufferData(GL_ARRAY_BUFFER,sizeof(vertices4),vertices4,GL_STATIC_DRAW);

attr_vertex = glGetAttribLocation(shader_data.psId, "a_position");

glVertexAttribPointer(attr_vertex, 2 , GL_FLOAT, GL_FALSE ,0, 0);

glEnableVertexAttribArray(attr_vertex);

glDrawArrays(GL_TRIANGLE_FAN,0,4);

glUniform1i(glGetUniformLocation(shader_data.psId,"index"),1);

glVertexAttribPointer(attr_vertex, 2 , GL_FLOAT, GL_FALSE ,0,(void *)(32) );

glDrawArrays(GL_TRIANGLE_FAN,0,4);

glUniform1i(glGetUniformLocation(shader_data.psId,"index"),2);

glVertexAttribPointer(attr_vertex, 2 , GL_FLOAT, GL_FALSE ,0,(void *)(64) );

glDrawArrays(GL_TRIANGLE_FAN,0,4);

In this case it draws all the 3 squares with dark red color.

4

1 回答 1

2 
uniform isamplerBuffer sampler;
glTexBuffer(GL_TEXTURE_BUFFER, GL_R8, bufferid);

你的问题是：它们不匹配。

您将纹理的存储创建为无符号 8 位整数，读取时将其标准化为浮点数。但是你告诉着色器你给了它有符号的 8 位整数，这些整数将被读取为整数，而不是浮点数。

您因不一致而混淆了 OpenGL。采样器类型与纹理格式不匹配会产生未定义的行为。

那应该是一个samplerBuffer，而不是一个isamplerBuffer。

于 2012-10-11T08:04:51.187 回答