Texture scaling/rotation

[Rick]

Does anyone have any code to scale/rotate a texture painted on a model? Say just a cube?

[Masterxilo]

I do this for uv scaling (move the mouse to set the uv scaling on the oil drum):

#include "engine.h"
#include "mathlib.h"

#include <string>
using namespace std;

void ScaleMeshUV(TEntity mesh, TVec2 uvscale)
{
for (int iSurf = 1; iSurf <= CountSurfaces(mesh); iSurf++)
{
	TSurface surface = GetSurface(mesh, iSurf);
	for (int iVert = 0; iVert < CountVertices(surface); iVert++)
	{
		for (int texcset = 0; texcset < 2; texcset++)
		{
			TVec2 uv = GetVertexTexCoords(surface, iVert, texcset) * uvscale;
			SetVertexTexCoords(surface, iVert, uv, texcset);
		}
	}
}
UpdateMesh(mesh);
}


int main(void)
{
// Init
Initialize();
Graphics(640,480);
TEntity world = CreateWorld();
TEntity buffer = CreateBuffer(640,480,BUFFER_COLOR0|BUFFER_DEPTH|BUFFER_NORMAL|BUFFER_COLOR2);

// Cam
TEntity camera = CreateCamera();
MoveEntity(camera, Vec3(0,0.5,-1.5) );

// Light
TEntity light  = CreateSpotLight(15,0);
MoveEntity   (light,  Vec3(-1,5,-4) );
RotateEntity (light,  Vec3(45,0,0), 0);
SetShadowmapSize(light,512);
AmbientLight(Vec3(.05));

// Ground
TEntity plane  = CreateCube(0);
ScaleEntity  (plane,  Vec3(100,1,100) );
MoveEntity   (plane,  Vec3(0,-2.5,0) );

// Model
TEntity m1 = LoadMesh("abstract::oildrum.gmf");
// ScaleMeshUV(m1, Vec2(3,2)); // some test scaling

// Main Loop
while(!KeyHit(KEY_ESCAPE) && !AppTerminate())
{
	TVec2 scale = Vec2((1.0f*Max(MouseX(),1)/GraphicsWidth())*10,(1.0f*Max(MouseY(),1)/GraphicsHeight())*10);
	ScaleMeshUV(m1, scale);

	UpdateWorld();

	SetBuffer(buffer);
	RenderWorld();
	SetBuffer(BackBuffer());
	RenderLights(buffer);

	ScaleMeshUV(m1, Vec2(1,1)/scale); // undo above scaling

	Flip(1);
}

// Terminate
return Terminate();
}

[Masterxilo]

And I just wrote this for rotation (press the up/down keys to rotate the texture on the oil drum):

#include "engine.h"
#include "mathlib.h"

#include <string>
using namespace std;

void RotateMeshUV(TEntity mesh, TVec2 rotationCenter, float angle)
{
angle = deg2rad(angle);
for (int iSurf = 1; iSurf <= CountSurfaces(mesh); iSurf++)
{
	TSurface surface = GetSurface(mesh, iSurf);
	for (int iVert = 0; iVert < CountVertices(surface); iVert++)
	{
		for (int texcset = 0; texcset < 2; texcset++)
		{
			TVec2 uv = GetVertexTexCoords(surface, iVert, texcset);
			uv -= rotationCenter;
			TVec2 rf = Vec2(cos(angle), sin(angle)); // roationFactor
			uv = Vec2(uv.X*rf.X - uv.Y*rf.Y, uv.X*rf.Y + uv.Y*rf.X);
			uv += rotationCenter;

			SetVertexTexCoords(surface, iVert, uv, texcset);
		}
	}
}
UpdateMesh(mesh);
}


int main(void)
{
// Init
Initialize();
Graphics(640,480);
TEntity world = CreateWorld();
TEntity buffer = CreateBuffer(640,480,BUFFER_COLOR0|BUFFER_DEPTH|BUFFER_NORMAL|BUFFER_COLOR2);

// Cam
TEntity camera = CreateCamera();
MoveEntity(camera, Vec3(0,0.5,-1.5) );

// Light
TEntity light  = CreateSpotLight(15,0);
MoveEntity   (light,  Vec3(-1,5,-4) );
RotateEntity (light,  Vec3(45,0,0), 0);
SetShadowmapSize(light,512);
AmbientLight(Vec3(.05));

// Ground
TEntity plane  = CreateCube(0);
ScaleEntity  (plane,  Vec3(100,1,100) );
MoveEntity   (plane,  Vec3(0,-2.5,0) );

// Model
TEntity m1 = LoadMesh("abstract::oildrum.gmf");
float angle = 0.0f;

// Main Loop
while(!KeyHit(KEY_ESCAPE) && !AppTerminate())
{
	if(KeyDown(KEY_UP) || KeyDown(KEY_DOWN))
	{
		float fac = KeyDown(KEY_UP) - KeyDown(KEY_DOWN);
		RotateMeshUV(m1, Vec2(0,0), fac);
		angle += fac;
	}

	UpdateWorld();

	SetBuffer(buffer);
	RenderWorld();
	SetBuffer(BackBuffer());
	RenderLights(buffer);

	DrawText(0,0,"angle: %f", angle);


	Flip(1);
}

// Terminate
return Terminate();
}

[Rick]

Very nice. I'll put this in my Thingoids. Thanks!

[Masterxilo]

Might actually be useful to define a center for scaling as well. Here some updated versions:

void ScaleMeshUV(TEntity mesh, TVec2 uvscale, TVec2 center = Vec2(0,0))
{
   for (int iSurf = 1; iSurf <= CountSurfaces(mesh); iSurf++)
   {
       TSurface surface = GetSurface(mesh, iSurf);
       for (int iVert = 0; iVert < CountVertices(surface); iVert++)
       {
           for (int texcset = 0; texcset < 2; texcset++)
           {
               TVec2 uv = (GetVertexTexCoords(surface, iVert, texcset) - center) * uvscale + center;
               SetVertexTexCoords(surface, iVert, uv, texcset);
           }
       }
   }
   UpdateMesh(mesh);
}


void RotateMeshUV(TEntity mesh, float angle, TVec2 center = Vec2(0,0))
{
   angle = deg2rad(angle);
   for (int iSurf = 1; iSurf <= CountSurfaces(mesh); iSurf++)
   {
       TSurface surface = GetSurface(mesh, iSurf);
       for (int iVert = 0; iVert < CountVertices(surface); iVert++)
       {
           for (int texcset = 0; texcset < 2; texcset++)
           {
               TVec2 uv = GetVertexTexCoords(surface, iVert, texcset);
               uv -= center;
               TVec2 rf = Vec2(cos(angle), sin(angle)); // roationFactor
               uv = Vec2(uv.X*rf.X - uv.Y*rf.Y, uv.X*rf.Y + uv.Y*rf.X);
               uv += center;

               SetVertexTexCoords(surface, iVert, uv, texcset);
           }
       }
   }
   UpdateMesh(mesh);
}