LWJGL OpenGL使用纹理图集UV坐标绘制文本

Question

I'm trying to draw text in my OpenGL program, using textured quads. My texture's dimension is 256x32 and each character is roughly 6 pixels large. (I got 42 characters per 'row', and 5 rows.)

When generating the UV coordinate for let's say the top-left character, I do this:

float textureDelta = 1.0f / 42.0f //0.0238
float u = 0;
float v = 0;

glBegin(GL_QUADS);
glTexCoord2f(u,1-v); glVertex2f(0,0);
glTexCoord2f(u+textureDelta, 1-v); glVertex2f(16,0);
glTexCoord2f(u+textureDela, 1-v + textureDelta); glVertex2f(16,16);
glTexCoord2f(u, 1-v+textureDelta); glVertex2f(0,16);
glEnd();

The problem I get is that my V coordinates seems entierly wrong, and the v coordinate seems to always be at the bottom, how do I fix this?

also, how do I deal with spaces?

Answer 1

That looks ok for the u coordinate. But since you have only 5 rows in the v direction, you need a different delta for that coordinate that is calculated based on the number of rows:

float uDelta = 1.0f / 42.0f;
float vDelta = 1.0f / 5.0f;

glTexCoord2f(u, 1.0f - v); ...
glTexCoord2f(u + uDelta, 1.0f - v); ...
glTexCoord2f(u + uDelta, 1.0f - v + vDelta); ...
glTexCoord2f(u, 1.0f - v + vDelta); ...