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Paul Nicholls · Guest

Hi all,
I can get a texture to tile across a triangle strip (quad) ok if the
texture tiles from the lower left edge (0,0,0) like so:

// quad vertices positions
// 4 - 3
// | |
// 1 - 2
//
glBegin(GL_TRIANGLE_STRIP);
x := cArenaScale * Vertex2.x;
y := FArenaBoundary.FArenaHeight;
z := cArenaScale * Vertex2.z;

glTexCoord2d(Edge.EdgeLength/cWallTextureWidth,FArenaBoundary.FArenaHeight/cWallTextureHeight);
glVertex3f(x,y,z); //3

x := cArenaScale * Vertex1.x;
y := FArenaBoundary.FArenaHeight;
z := cArenaScale * Vertex1.z;

glTexCoord2d(0,FArenaBoundary.FArenaHeight/cWallTextureHeight);
glVertex3f(x,y,z); //4

x := cArenaScale * Vertex2.x;
y := 0;
z := cArenaScale * Vertex2.z;

glTexCoord2d(Edge.EdgeLength/cWallTextureWidth,0);
glVertex3f(x,y,z); //2

x := cArenaScale * Vertex1.x;
y := 0;
z := cArenaScale * Vertex1.z;

glTexCoord2d(0,0); glVertex3f(x,y,z); //1
glEnd;

But I am having a dickens of a time trying to make a texture tile across a
triangle strip (quad) if the centre of the strip is at (0,0,0) and I want
the texturing to start from the center of the quad.

Here is some ASCII art to hopefull help :)

(MinX,0,MinZ)

o--------------

Paul Nicholls · Guest

<SNIP>

Thanks guys, but I have figured it out :)

// Min/Max X and Z are the extents of the tri strip/quad that I want to
draw tiled

MinX := FArenaBoundary.BoundingBox.MinX;
MaxX := FArenaBoundary.BoundingBox.MaxX;
MinZ := FArenaBoundary.BoundingBox.MinZ;
MaxZ := FArenaBoundary.BoundingBox.MaxZ;

// workout the texture scaling factor for the x and z direction
FloorScaleX := (MaxX - MinX) / cFloorTextureWidth;
FloorScaleZ := (MaxZ - MinZ) / cFloorTextureHeight;

// Draw Floor
glBindTexture(GL_TEXTURE_2D,FTextures[1]);

// 4 - 3
// | |
// 1 - 2
//
glBegin(GL_TRIANGLE_STRIP);
glTexCoord2d(+0.5*FloorScaleX,+0.5*FloorScaleZ);
glVertex3f(MaxX,0,MinZ); //3

glTexCoord2d(-0.5*FloorScaleX,+0.5*FloorScaleZ);
glVertex3f(MinX,0,MinZ); //4

glTexCoord2d(+0.5*FloorScaleX,-0.5*FloorScaleZ);
glVertex3f(MaxX,0,MaxZ); //2

glTexCoord2d(-0.5*FloorScaleX,-0.5*FloorScaleZ);
glVertex3f(MinX,0,MaxZ); //1
glEnd;

Hope this helps someone else :-)

cheers,
Paul.

Jeremy Darling · Guest

Paul,
I'm curious why your not using GLScene for something like this. It
definately makes your life easier when it comes to OpenGL in Delphi and
speeds the development time.

Jeremy

"Paul Nicholls" <paul_nicholls (AT) hotmail (DOT) NOSPAM.com> wrote

Paul Nicholls · Guest

"Jeremy Darling" <jdarling (AT) eonclash (DOT) com> wrote

Jeremy Darling · Guest

Yes you can use GLScene in a commercial application. It falls under the MPL
(Mozilla Public License, http://www.mozilla.org)

Jeremy

"Paul Nicholls" <paul_nicholls (AT) hotmail (DOT) NOSPAM.com> wrote