Problem in dynamic loop

OpenGL
1

hi.

I’m learning about GLSL.
Appearing below is a GLSL fragment source code I wrote for experiment.

uniform int			N_LOOP;
void main(void)
{
	int i;
	float tmp=0.0f;
	for(i=0; i<N_LOOP; i++){
		tmp	+= 0.1f;
	}
	gl_FragColor	= vec4(tmp, 0.0, 0.0, 0.0);
}

And, I set N_LOOP by written the below code.

glUniform1iARB(glGetUniformLocationARB(_programObject, "N_LOOP"), nLoop);

I think that the result of this program is depend on nLoop but the result I got was similar to vec4(0.1, 0.0, 0.0, 0.0).
It seems that for-loop doesn’t works dynamically.

Does GLSL support dynamic loop like I used above ?
(Is this written in specification or FAQ ?
I didn’t find such description.)

Would you please give me some advice ?
Thanks.

P.S.
My execution environment is GeForce6800GT(AGP).
When I wrote same program in HLSL and executed, the result is similar to (0.1*N_LOOP, 0.0, 0.0, 0.0).

2

Should work. What driver are you running?

You have errors.

0.1f should be 0.1
Get rid of the "f"s and turn on strict GLSL support with NVEmulate.

3

Thanks V-man.

I changed code from 1.0f to 1.0, and executed program.
As a result, I got a correct result.
Then, I changed code from 1.0 to 1.0f for confirmation.
As a result, I got a correnct result, too.

I don’t understand why my code works correctly, but it is truth that result is correctly.
I hated to bother you about this.

4

What is the value of N_LOOP?

The GLSL spec says

The consequences of very long or non-terminating loops are platform dependent.
On your hardware, the max count loop is 255. If you exceed this limit, no error is generated but the results are undefined.

Greetz,

N.

5

This topic was automatically closed 183 days after the last reply. New replies are no longer allowed.