# linear texture mapping - perspective correct

This topic is 3627 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

I posted about a week ago asking about texture coordinates, and was told that before I try perspective correct, that I should be able to do linear mapping. I've finished making my program do linear mapping, but it looks really bad. Mapping onto a square made of two triangles makes straight lines look bent at certain angles. Anyways, what's the next step? I have done my texturing by assigning texture coords to each vertex that range from 0 to 1(the width/height of the texture), and linear interpolating the texture coords down the edges, and then between the edges. I've read in many places that a formula with 1/z u/z and v/z fit in here somewhere. Can someone explain? Thanks again =) edit: here is the relevant code from my project... //when edge is added: y_steps = int(GET

.edges[v].pt[1][1] - GET

.edges[v].pt[0][1]); GET

.edges[v].u_inc = (GET

.edges[v].p_texcoord[1][0] - GET

.edges[v].p_texcoord[0][0]) / (float)y_steps; GET

.edges[v].v_inc = (GET

.edges[v].p_texcoord[1][1] - GET

.edges[v].p_texcoord[0][1]) / (float)y_steps; GET

.edges[v].U = GET

.edges[v].p_texcoord[0][0]; GET

.edges[v].V = GET

.edges[v].p_texcoord[0][1]; //when edges are updated, per scanline: GET

.left_edge->V += GET

.left_edge->v_inc; GET

.left_edge->U += GET

.left_edge->u_inc; GET

.right_edge->V += GET

.right_edge->v_inc; GET

.right_edge->U += GET

.right_edge->u_inc; //when rendered: for(sx = (int)GET

.left_edge->x_int; sx <= (int)GET

.right_edge->x_int; sx++) { if(sx >= 0 && sx < SCREENWIDTH) { pixel_x = (((sx - GET

.left_edge->x_int) / (GET

.right_edge->x_int GET

.left_edge->x_int)) * (GET

.right_edge->U - GET

.left_edge->U) + GET

.left_edge->U) * bm_texture.bmWidth; pixel_y = (1-(((sx - GET

.left_edge->x_int) / (GET

.right_edge->x_int - GET

.left_edge->x_int)) * (GET

.right_edge->V - GET

.left_edge->V) + GET

.left_edge->V)) * bm_texture.bmHeight; if(pixel_y < 0) pixel_y = 0; if(pixel_x < 0) pixel_x = 0; p_bits[(SCREENWIDTH * sy) + sx] = t_bits[(bm_texture.bmWidth * pixel_y) + pixel_x]; } }

##### Share on other sites
I found this article on perspective correct interpolation, but right after Figure 2, (1), (2), ect, I am lost. I can't figure out what those fomulas mean, or how to apply them to what Im doing...Can anyone help?

the article:
http://www.comp.nus.edu.sg/~lowkl/publications/lowk_persp_interp_techrep.pdf

Thanks, Nick

##### Share on other sites
never mind...got it.

1. 1
2. 2
Rutin
16
3. 3
4. 4
5. 5

• 26
• 11
• 9
• 9
• 11
• ### Forum Statistics

• Total Topics
633709
• Total Posts
3013481
×