# question about uv in valve's bsp map files

This topic is 4329 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

hello guys, i'm tring to extract the bsp map file of half-life2, but i really got confused about the uv coordinate of the face. according to the article found here http://www.geocities.com/cofrdrbob/ , the half-life2's map does not use uv coordinate directly. it adopts two vectors to define a plane that is parallel to the texture. to get the uv coordinate, one need to project the model face on that plane. here is the structure of the texture info in the map:
struct texinfo_t
{
float       textureVecs[2][4];      // [s/t][xyz offset]
float       lightmapVecs[2][4];     // [s/t][xyz offset] - length is in units of texels/area
int         flags;                  // miptex flags + overrides
int         texdata;                // Pointer to texture name, size, etc.
}

and also some explanation about this found at flipcode: Textures are applied to faces using a planar texture mapping scheme. Instead of specifying texture coordinates for each of the vertices of the face, two texture axes are specified which define a plane. Texture coordinates are generated by projecting the vertices of the face onto this plane. While this may seem to add some complexity to the task of the programmer, it greatly reduces the burden of the level designer in aligning textures across multiple faces. The texture coordinates (u, v) for a point(x, y, z) are found using the following computation: u = x * u_axis.x + y * u_axis.y + z * u_axis.z + u_offset v = x * v_axis.x + y * v_axis.y + z * v_axis.z + v_offset and this is the function i use to get the uv coordinate, the x,y,z is the position of the face in world coordinate.
void getUV(float x,float y,float z,float &u,float &v,struct texinfo_t tempTexInfo)
{
u=tempTexInfo.textureVecs[0][0]*x+tempTexInfo.textureVecs[0][1]*y+tempTexInfo.textureVecs[0][2]*z+tempTexInfo.textureVecs[0][3];
v=tempTexInfo.textureVecs[1][0]*x+tempTexInfo.textureVecs[1][1]*y+tempTexInfo.textureVecs[1][2]*z+tempTexInfo.textureVecs[1][3];
}

but the question is that what i got from the file is something like this:
vt -18816.000000 18.417999 0
vt -18816.000000 -320.000000 0
vt -19632.000000 -320.000000 0
vt -18432.000000 18.417999 0
vt -18529.759766 18.417999 0
vt -18529.759766 -320.000000 0
vt -18432.000000 -320.000000 0
vt -8958.240234 18529.759766 0
vt -9023.480469 19639.240234 0
vt -8384.000000 19920.000000 0
vt -7808.000000 19680.000000 0
vt -8384.000000 19920.000000 0
vt -9023.480469 19639.240234 0
vt -8958.240234 18529.759766 0
vt -7808.000000 19680.000000 0
vt -19639.240234 18.417999 0
vt -18529.759766 18.417999 0
vt -18529.759766 -320.000000 0
vt -19639.240234 -320.000000 0
vt -8384.000000 18.417999 0
vt -9023.480469 18.417999 0
vt -9023.480469 -320.000000 0
vt -8384.000000 -320.000000 0
vt -18529.759766 18.417999 0
vt -19680.000000 18.417999 0
vt -19680.000000 -320.000000 0
vt -18529.759766 -320.000000 0
vt -7808.000000 18.417999 0
vt -8384.000000 18.417999 0

the uv coordinate should be float between 0 and 1, but i do not know why i have these large numbers and even some negative ones. i also print out the vector used to define the texture plane in the file, they are like this:
s:[x:0.000000,y:4.000000,z:0.000000,o:63.980999]
t:[x:4.000000,y:0.000000,z:0.000000,o:0.000000]
s:[x:-4.000000,y:0.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:-4.000000,y:0.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:-256.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:63.980999]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:127.981003]
t:[x:0.000000,y:0.000000,z:-4.000000,o:-256.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:-256.000000]
s:[x:1.000000,y:0.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-1.000000,o:0.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:63.980999]
t:[x:4.000000,y:0.000000,z:0.000000,o:0.000000]
s:[x:-4.000000,y:0.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:63.980999]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:-256.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:63.981400]
t:[x:4.000000,y:0.000000,z:0.000000,o:0.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:63.981400]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:4.000000,y:0.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:0.000000,y:-4.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:0.000000,y:1.000000,z:0.000000,o:0.000000]
t:[x:1.000000,y:0.000000,z:0.000000,o:0.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:191.981003]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:4.000000,y:0.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:-4.000000,z:0.000000,o:0.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:448.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:-4.000000,y:0.000000,z:0.000000,o:384.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:0.000000,y:-4.000000,z:0.000000,o:-63.981400]
t:[x:4.000000,y:0.000000,z:0.000000,o:0.000000]
s:[x:0.000000,y:-1.000000,z:0.000000,o:0.000000]
t:[x:1.000000,y:0.000000,z:0.000000,o:0.000000]
s:[x:0.000000,y:-4.000000,z:0.000000,o:-63.981400]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:0.000000,y:-4.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:0.000000,y:1.000000,z:0.000000,o:0.000000]
t:[x:1.000000,y:0.000000,z:0.000000,o:0.000000]
s:[x:0.000000,y:-4.000000,z:0.000000,o:-63.980999]
t:[x:4.000000,y:0.000000,z:0.000000,o:0.000000]
s:[x:0.000000,y:-1.000000,z:0.000000,o:0.000000]
t:[x:1.000000,y:0.000000,z:0.000000,o:0.000000]
s:[x:0.000000,y:-4.000000,z:0.000000,o:-320.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:0.000000,y:-4.000000,z:0.000000,o:-319.980988]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:447.980988]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:0.000000]
t:[x:4.000000,y:0.000000,z:0.000000,o:0.000000]
s:[x:-4.000000,y:0.000000,z:0.000000,o:-32.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:-4.000000,y:0.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:256.000000]
s:[x:0.000000,y:-4.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:256.000000]
s:[x:4.000000,y:0.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:256.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:256.000000]
s:[x:4.000000,y:0.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:-4.000000,z:0.000000,o:256.000000]
s:[x:1.000000,y:0.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:-1.000000,z:0.000000,o:0.000000]
s:[x:-4.000000,y:0.000000,z:0.000000,o:448.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:0.000000,y:4.000000,z:0.000000,o:511.980988]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:1.000000,y:0.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-1.000000,o:0.000000]
s:[x:0.000000,y:-4.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:0.000000,z:-4.000000,o:0.000000]
s:[x:4.000000,y:0.000000,z:0.000000,o:0.000000]
t:[x:0.000000,y:-4.000000,z:0.000000,o:0.000000]


##### Share on other sites
The texture coordinates generated aren't normalized AFAIK. You need to divide them by the texture size. Although they still won't be in the [0, 1] range because you may get a texture repeated across a single face.

##### Share on other sites
You need to normalize the coordinates to the texture size like Monder mentioned, although you shouldn't have to worry about coordinates outside the range [0,1]. The textures are supposed to repeat, so set your texture addressing mode to D3DTADDRESS_WRAP (DirectX) or the GL_TEXTURE_WRAP_S/GL_TEXTURE_WRAP_T texture parameters to GL_REPEAT (OpenGL), and everything works out fine.

##### Share on other sites
thanks, so you mean i should divide the the vector by the size of the texture map?

i'll have a try.
but how if i still get negative uv coordinates?

thanks again

##### Share on other sites
Negative coordinates just work like positive ones, i.e. you just get wrapping, so if you had a face with a -1 coord at one end at 1 at the other your texture would repeat twice just the same as if the coordinates had been 0 and 2.

##### Share on other sites
thank you, it works! just, the texture is kinda upside-down, guess i can fix it later. thank you guys again.