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strip blitting + image offsets == trouble

 
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Zettablade



Joined: 05 May 2006
Posts: 71
PostPosted: Fri Nov 03, 2006 2:40 pm    Post subject: strip blitting + image offsets == trouble Reply with quote
For some reason, my blitting function isn't working. It doesn't resize properly when I change the width or height, and I get weird results when the offsets are changed. Anyone know what I'm doing wrong?

Code:
void drawImageFast(float x, float y, float width, float height, float u0, float u1, float v0, float v1, IMAGE *img)
{
   float ii = 0;
   short slice = 32;

   sceGuTexImage(0,img->realWidth,img->realHeight,img->realWidth,(void*)img->data);
   
   for(i = 0; ii < u1; ii += slice) {
      VertexUV* vertices = (VertexUV*)sceGuGetMemory(2 * sizeof(VertexUV));

      slice = 32;

      if (ii + slice > u1) slice = width - ii;

      vertices[0].u = u0 + ii;
      vertices[0].v = v0;
      vertices[0].x = x + ii;
      vertices[0].y = y;

      vertices[1].u = u0 + ii + slice;
      vertices[1].v = v0 + v1;
      vertices[1].x = x + ii + slice;
      vertices[1].y = y + height;
      
      sceGuDrawArray(GU_SPRITES, GU_TEXTURE_32BITF|GU_VERTEX_32BITF|GU_TRANSFORM_2D, 2, 0, vertices);
   }
}
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hlide



Joined: 10 Sep 2006
Posts: 750
PostPosted: Fri Nov 03, 2006 5:15 pm    Post subject: Reply with quote
I can read in /pspsdk/gu/doc/commands.txt :
Quote:
Floats processed in the command-stream are 24 bits instead of 32 that are
used by the CPU. Conversion from 32 to 24 bits is done by shifting the
value down 8 bits, losing the least significant bits of the mantissa.


if it does so and have 256.0 as a float value, would it be converted into 1.0 because of losing the least significant bits of the mantissa !?

Well, I'm totaly new with GU but I hope you will find your error and share your solution :)
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