Scaling models... easy but where is my fault?

LuMo · Post by **LuMo** » Fri May 19, 2006 8:36 pm

i just want to scale a model for psp to fit the screen
using the code below does scale, but it does not keep aspect ratio

if someone finds my mistake please point me towards it

Thanks in Advance
lumo

Code: Select all

minX = lmesh.verticesV3&#91;0&#93;.x; // init...
        minY = lmesh.verticesV3&#91;0&#93;.y;
        minZ = lmesh.verticesV3&#91;0&#93;.z;
        maxX = lmesh.verticesV3&#91;0&#93;.x;
        maxY = lmesh.verticesV3&#91;0&#93;.y;
        maxZ = lmesh.verticesV3&#91;0&#93;.z;

        for&#40; unsigned long idx = 1; idx<lmesh.vertexCount; idx++ &#41;
        &#123;
          minX = min&#40;minX, lmesh.verticesV3&#91;idx&#93;.x&#41;;
          minY = min&#40;minY, lmesh.verticesV3&#91;idx&#93;.y&#41;;
          minZ = min&#40;minZ, lmesh.verticesV3&#91;idx&#93;.z&#41;;
          maxX = max&#40;maxX, lmesh.verticesV3&#91;idx&#93;.x&#41;;
          maxY = max&#40;maxY, lmesh.verticesV3&#91;idx&#93;.y&#41;;
          maxZ = max&#40;maxZ, lmesh.verticesV3&#91;idx&#93;.z&#41;;
        &#125;	    	
				// resize values
				sizeX = maxX - minX;
				sizeY = maxY - minY;
				sizeZ = maxZ - minZ;
				
				// write new values
				for &#40;unsigned int i=0;i<lmesh.vertexCount;i++&#41;
				&#123;
					lmesh.verticesV3&#91;i&#93;.x = &#40;lmesh.verticesV3&#91;i&#93;.x/sizeX&#41;*scaleX;
					lmesh.verticesV3&#91;i&#93;.y = &#40;lmesh.verticesV3&#91;i&#93;.y/sizeY&#41;*scaleY;
					lmesh.verticesV3&#91;i&#93;.z = &#40;lmesh.verticesV3&#91;i&#93;.z/sizeZ&#41;*scaleZ;
				&#125;

groepaz · Post by **groepaz** » Fri May 19, 2006 8:52 pm

Code: Select all

        minY = lmesh.verticesV3&#91;0&#93;.y; 
        minZ = lmesh.verticesV3&#91;0&#93;.z; 
        maxX = lmesh.verticesV3&#91;0&#93;.x; 
        maxY = lmesh.verticesV3&#91;0&#93;.y; 
        maxZ = lmesh.verticesV3&#91;0&#93;.z;

that somehow looks wrong to me (min and max will be same)

anyway, any reason why you dont use a matrix to scale?

LuMo · Post by **LuMo** » Fri May 19, 2006 9:02 pm

this (the code you marked) only sets the initial values;
i do not use a matrix cause i scale the model before i load it to psp
so the calculation is just to resize while model is on PC

groepaz · Post by **groepaz** » Fri May 19, 2006 9:06 pm

ah ok i see. cant see an obvious error then either *shrug*

tried with a simple modell (like a cube) ? thats what i usually do to see what really happens

ufoz · Post by **ufoz** » Fri May 19, 2006 9:08 pm

It doesn't keep the aspect ratio because you're normalizing the entire model into the (-1,1) cube and then scaling that with scaleX,Y,Z
So your output will have the same ratio that scaleX,Y,Z have.

gsus · Post by **gsus** » Sat May 20, 2006 4:56 am

seawas...

your model is between [min max]
tranform it first, so the midpoint is at coordinate origin
widht pos = pos-(max+min)/2, so its between [-(min+max)/2 (min+max)/2]
now you can scale it with pos = pos*2*scale/size.. and your is in [-scale scale]

also it might depend on your projecion matrices..

regards, gsus

LuMo · Post by **LuMo** » Sat May 20, 2006 5:44 am

my model is already centered (done before)
i changed the code today, did not test the result, if mine fails again, ill try yours; let you know later
thanks for help

Saotome · Post by **Saotome** » Sat May 20, 2006 6:29 am

If you didn't already solve it, your problem seems to be, that you're scaling each aixs with it's maximum (i.e. each axis with a different value). But you should scale all axes with just one maximum. -> find the max of sizeX,sizeY and sizeZ, and scale by that one value.

LuMo · Post by **LuMo** » Sat May 20, 2006 6:34 am

yeah! thats was my fault!
thanks :))