View Full Version : Texture droppings

Robin Forster
12-13-2001, 12:03 PM

I have a simplae engine that renders a rotating brick wall with a text blurb on one side. I render the text and then fragment the image into gl sized textures when necessary. I notice little glitches on the rendered face with the text. I am sure it is not my text rendering code due to the location of the glitches. Has anyone else experienced such glitches and do you know how to remedy the situation?


12-13-2001, 01:39 PM
This needs an image.

It could be border filtering, or aliasing, or T vertices, or z fighting. Difficult to tell without a more detailed description.

Robin Forster
12-13-2001, 02:52 PM
The code is simple I set a basic viewport with a basic ortho projection right out of the web tutorials (NeHe). I have two such contexts one for 3d and one for my 2d overlay (user interface - buttons etc). I have written what is essentially a 3d PowerPoint type slide presentation with neat 3d effects and lighting (my lighting is off at the moment). After setting the matrices I just texture map quads from a fragmented image (32x32 texel textures). I do so in a for loop and its basically just a bind then the normal then the texture coordinates and vertices. Text book code. :-)


Robin Forster
12-13-2001, 03:00 PM
It is important to note that the noticable effect of these droppings is in a location where adjacent textures are both solid black. Thats why its wierd.

12-13-2001, 09:57 PM
The topic of this thread really had me wonder about the digestive system of a texture for a second...

try GL_CLAMP_TO_EDGE instead of GL_CLAMP for the texture wrapping mode. However, you still might get artifacts. It might be better to render the whole thing as a single quad / tristrip with one texture. That'll be faster, too http://www.opengl.org/discussion_boards/ubb/wink.gif

12-14-2001, 07:32 AM
Ive got recently a problem on texture borders that is perhaps the same as your :
I used linear mode for textures and there were white lines in the border (with border set to 0 of course). It was because the engine wrapped the texture to get the texel for interpolation even if I CLAMPed texel coordinates. It was my fault, anyway, because I said the texture coordinates (GLfloat) to 0,0, where I should have said (0.5 , 0.5). I did it and then it looked perfectly.
Ivn't you do the same mistake ?

Robin Forster
12-14-2001, 01:56 PM
I have specified GL_CLAMP and that fixed the problem I tried GL_CLAMP_TO_EDGE as well but it did not work. I am wondering if my graphics card supports 1.2 commands. Anyhow the scene is cleared up now.

Thanks to all who responded!