Texturing a line with 2-D texture element

OpenGL OpenGL: Basic Coding
1

Hi Everyone,

I am trying to texture a line segment with a 2-D texture element. In other words, I am providing same u value and increasing v value for my line.

I try to do this in Cg (with this piece of code:

kd = (half3)tex2D(hairTexture, uv).xyz;

), what I want to know is that whether this is possible with the OpenGL part.

If it is possible to texture a line primitive with a 2-D texture element with pure OpenGL, then I would know that the problem is with Cg part. (Recommendations with the Cg part are also welcomed :slight_smile: )

Thanks in advance

Rifat

2 

glColor4f(1.0,1.0,1.0,1.0);
glEnable(GL_TEXTURE_2D);
glBegin(GL_LINES);
glTexcoord2f(u,v1);
glVertex3f(x1,y1,z1);
glTexcoord2f(u,v2);
glVertex3f(x2,y2,z2);
glEnd();
3

Then I understand that it is possible to texture a line primitive with GL_TEXTURE_2D and glTexcoord2f.

I am loading the texture, passing the texture identifier to Cg’s sampler2D variable and try to access texture information with

(half3)tex2D(hairTexture, uv).xyz;

Unfortunately, it does not seem to be reading correct color information; I cannot see texture drawn onto the line primitive.

Am I doing something wrong?

4

I guess so…the question is ‘what’ :wink:

Did you try the fixed function path? Are your sampler states correct? Try writing out the uv coords, maybe there’s something wrong with them, etc.

N.

5

Hmm “uv coords” may be the problem… I dynamically calculate them at vertex shader. I thought they were correct, but maybe… When I get to home I will give it a try and let you know…

Thanks anyway…

6

Maybe you did not build mipmaps for your texture, by default mipmaps are needed.