Get segment fault when I tried to drawPixels to GL_RGBA , please help!

OpenGL
1

I can draw pixels to RED, GREEN, BLUE and ALPHA partion by using:

GLubye buf[512][512];

glDrawBuffer(GL_FRONT);
glDrawPixels(512,512,GL_RED, GL_UNSIGNED_BYTE, buf)

But I encounter a segment fault when I tried to draw pixel to RGBA partion. The following is what my code look like:
GLuint buf[512][512];

glDrawBuffer(GL_FRONT);
glDrawPixels(512,512,GL_RGBA, GL_UNSIGNED_INT, buf)

What could be wrong here?

Please help! Thanks a lot

2

Well, you need an int for each red, green, blue, and alpha value. So you must allocate four ints for each pixel, i.E.:

GLuint buf[512][512][4];

3

That would be a 4sizeof(int)=432=128bit framebuffer.So a byte for each component should do.

GLubyte buf[512][512][4];
or
char buf[5125124]

4

Yes, if the command to draw pixels is invoked with (darron used GL_UNSIGNED_INT):

glDrawPixels(512, 512, GL_RGBA, GL_UNSIGNED_BYTE, buf)

This makes more sense anyway, since the accuracy of unsigned int is overkill anyway, and will slow down rendering.

5

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