🔒 Locked

Texturing triangle fans problem

Started by i_luv_cplusplus Jun 30, 2007 at 7:11 AM 10 replies 1.5k views

Original Post

Jun 30, 2007 at 7:11 AM

hello, after a long fight with texturing my terrain made out of triangle fans, I surrender. Anyone knows the reason for such buggy texture mapping (look at picture)? http://i13.tinypic.com/543ss54.jpg

Gage64

135

Gage64

Jun 30, 2007 at 8:19 AM

Try using a different texture-addressing mode. Can you post the code that calculates the texture coordinates?

i_luv_cplusplus

Author

i_luv_cplusplus

Jun 30, 2007 at 8:53 AM

My terrain is a 289x289 heightmap, divided into 289 17x17 patches. Here's the temporary terrain rendering code... (mesh is rendered correctly, only texturing isn't working)

texture size is 289x289, I want it to be stretched across the whole terrain

        for (int pZ=0;pZ<289;pZ+=16)        {            for (int pX=0;pX<289;pX+=16)            {                for (int fZ=pZ+(lod-1)/2;fZ<pZ+17;fZ+=(lod-1))                {                    for (int fX=pX+(lod-1)/2;fX<pX+17;fX+=(lod-1))                    {                        glBegin(GL_TRIANGLE_FAN);                        RenderVertex(fX, fZ);                        RenderVertex((fX-(lod-1)/2), (fZ-(lod-1)/2));                        RenderVertex(fX, (fZ-(lod-1)/2));                        RenderVertex((fX+(lod-1)/2), (fZ-(lod-1)/2));                        RenderVertex((fX+(lod-1)/2), fZ);                        RenderVertex((fX+(lod-1)/2), (fZ+(lod-1)/2));                        RenderVertex(fX, (fZ+(lod-1)/2));                        RenderVertex((fX-(lod-1)/2), (fZ+(lod-1)/2));                        RenderVertex((fX-(lod-1)/2), fZ);                        RenderVertex((fX-(lod-1)/2), (fZ-(lod-1)/2));                        glEnd();                    }                }            }        }void CTerrain::RenderVertex(int x, int z){    float tX, tZ;    tX = (x/289);    tZ = (z/289);    glTexCoords2f(tX, tZ);    glVertex3f(x*TileSize, GetTrueHeightAtPoint(x, z), z*TileSize);};

EDIT: Lod is integer value equal to 3/5/9 depending on my level of detail needs

rotalever

Jun 30, 2007 at 9:07 AM

Are your textures repeated or clamped (to edge)?
(show us the part where you set up the texture image)

i_luv_cplusplus

Author

i_luv_cplusplus

Jun 30, 2007 at 9:10 AM

glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

and it was doing fine when my terrain was based off triangle strips :|

Gage64

135

Gage64

Jun 30, 2007 at 9:17 AM

But what address mode are you using? Do you make the following calls:

glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);

somewhere in your code? If you're not then add them, and try setting the last parameter to GL_REPEAT.

i_luv_cplusplus

Author

i_luv_cplusplus

Jun 30, 2007 at 9:25 AM

Setting it to REPEAT didn't change anything, but when I set it to CLAMP, everything that was solid green on the screenshot, became black, while the rest remained same

rotalever

Jun 30, 2007 at 11:05 AM

In RenderVertex()
Try changing
tX = (x/289);
to
tX = 1.0*x/289.0;

same with tZ of course....

i_luv_cplusplus

Author

i_luv_cplusplus

Jun 30, 2007 at 1:37 PM

hmm after some changes, I made it work, problem solved but...
interesting

is there some rule, that you can't bind/change rendering modes AFTER glBegin but BEFORE any glVertex calls? because this:

{  glDisable(GL_TEXTURE_2D);  glBegin(GL_TRIANGLE_FAN);  RenderVertex()}void CTerrain::RenderVertex(int x, int z){    float tX, tZ;    tX = (1.0*x/289.0);    tZ = (1.0*z/289.0);    glEnable(GL_TEXTURE_2D);    glBindTexture(GL_TEXTURE_2D, grass.ID);    glTexCoord2f(tX, tZ);    glVertex3f(x*TileSize, GetTrueHeightAtPoint(x, z)*0.01, z*TileSize);    verts++;};

doesn't show the texture, yet if I move the Enable and BindTexture before glBegin() it works flawlessly?

AndyEsser

108

AndyEsser

Jun 30, 2007 at 3:18 PM

You can't have glEnable() or glBindTexture between glBegin or glEnd. In fact I believe the only calls you can have are for vertex,texture and normal functions.

Jaiminho

Jun 30, 2007 at 5:29 PM

Quote:
Original post by AndyEsser
You can't have glEnable() or glBindTexture between glBegin or glEnd. In fact I believe the only calls you can have are for vertex,texture and normal functions.

From the manpages:

Quote:
Only a subset of GL commands can be used between glBegin and glEnd. The commands are glVertex, glColor, glIndex, glNormal, glTexCoord, glEvalCoord, glEvalPoint, glArrayElement, glMaterial, and glEdgeFlag. Also, it is acceptable to use glCallList or glCallLists to execute display lists that include only the preceding commands. If any other GL command is executed between glBegin and glEnd, the error flag is set and the command is ignored.

AndyEsser

108

AndyEsser

Jul 1, 2007 at 4:09 AM

I was close enough ;)

Topic Locked

This topic has been locked by a moderator. New replies are not allowed.