Hi ,here is my glsl code
Code :
#version 400
 
in vec4 ex_Color;
in vec4 ex_Pos;
out vec4 FragColor;
 
 
uniform sampler2D RayStartPoint;
uniform sampler2D RayStopPoint;
 
void main()
{
  vec4 temp = ex_Color;
  vec2 texc = ((ex_Pos.xy / ex_Pos.w) + 1.0f )/2.0f ;  
 
  vec4 startPosition  = texture(RayStartPoint, texc) ;
  vec4 stopPosition  = texture2D(RayStopPoint, texc);
   temp.w = 1 ;   
 
 // FragColor = startPosition ;
	FragColor = stopPosition ;
 // FragColor = temp ;
 
 //  FragColor = stopPosition -  startPosition ;
 
}
my program could find the first uniform location,but can't find the second. the function "glGetUniformLocation" just return -1
anyone had encountered similar problem?