Nehe Lesson 6 with transparent images (DevIL question)

Started by baegsi, January 24, 2005, 13:25:36

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baegsi

January 24, 2005, 13:25:36
I can't get the lwjgl-ported Nehe Lesson 6 with alpha transparency running :oops: .

This is the original code
..
IL.ilCopyPixels(0, 0, 0, 256, 256, 1, IL.IL_RGB, IL.IL_BYTE, scratch);
...
// Generate The Texture
GL11.glTexImage2D(
  GL11.GL_TEXTURE_2D,
  0, 
  GL11.GL_RGB, 
  IL.ilGetInteger(IL.IL_IMAGE_WIDTH),                   
  IL.ilGetInteger(IL.IL_IMAGE_HEIGHT), 
  0, 
  GL11.GL_RGB, 
  GL11.GL_UNSIGNED_BYTE, 
  scratch);
...


Now I just changed the format settings:

...
IL.ilCopyPixels(0, 0, 0, 256, 256, 1, IL.IL_RGBA/*<==*/, IL.IL_BYTE, scratch);
...
// Generate The Texture
GL11.glTexImage2D(
  GL11.GL_TEXTURE_2D,
  0, 
  GL11.GL_RGBA, /*<==*/
  IL.ilGetInteger(IL.IL_IMAGE_WIDTH),                   
  IL.ilGetInteger(IL.IL_IMAGE_HEIGHT), 
  0, 
  GL11.GL_RGBA, /*<==*/
  GL11.GL_UNSIGNED_BYTE, 
  scratch);
...


and loaded the example with a png with transparency, but it crashes with an exception.
What do I wrong? Any help very appreciated!

baegsi

#1
January 24, 2005, 13:36:22
Found the problem: "scratch" buffer too small. Instead of

QuoteByteBuffer scratch = ByteBuffer.allocateDirect(IL.ilGetInteger(IL.IL_IMAGE_WIDTH) * IL.ilGetInteger(IL.IL_IMAGE_HEIGHT) * 3);

I used:

QuoteByteBuffer scratch = ByteBuffer.allocateDirect(IL.ilGetInteger(IL.IL_IMAGE_WIDTH) * IL.ilGetInteger(IL.IL_IMAGE_HEIGHT) * 4 /*<==*/);

Hmh, I think I have to understand the whole xyBuffer stuff properly...  :oops:

Matzon

#2
January 24, 2005, 14:12:33
makes sense...
using RGB (no transparency) you use 3 Bytes per pixel (hence the 3) - adding the alpha channel (8 more bits, total 32) increases the size needed per pixel to 4 bytes.

K.I.L.E.R

#3
January 26, 2005, 11:43:28
Why not just use this?

ByteBuffer scratch = ByteBuffer.allocateDirect
        (
        		IL.ilGetInteger(IL.IL_IMAGE_BITS_PER_PIXEL) *
        		IL.ilGetInteger(IL.IL_IMAGE_DEPTH) *
        		IL.ilGetInteger(IL.IL_IMAGE_WIDTH) * 
        		IL.ilGetInteger(IL.IL_IMAGE_HEIGHT)
        );

CaptainJester

#4
January 26, 2005, 12:15:41
Quote from: "K.I.L.E.R"Why not just use this?

ByteBuffer scratch = ByteBuffer.allocateDirect
        (
        		IL.ilGetInteger(IL.IL_IMAGE_BITS_PER_PIXEL) *
        		IL.ilGetInteger(IL.IL_IMAGE_DEPTH) *
        		IL.ilGetInteger(IL.IL_IMAGE_WIDTH) * 
        		IL.ilGetInteger(IL.IL_IMAGE_HEIGHT)
        );

You mean IL_IMAGE_BYTES_PER_PIXEL
The problems of this world cannot possibly be solved by skeptics or cynics whose horizons are limited by the obvious realities.  We need men and women who can dream of things that never were. - John Fitzgerald Kennedy(35th US President)
8)

K.I.L.E.R

#5
January 26, 2005, 14:16:20
Quote from: "CaptainJester"
Quote from: "K.I.L.E.R"Why not just use this?

ByteBuffer scratch = ByteBuffer.allocateDirect
        (
        		IL.ilGetInteger(IL.IL_IMAGE_BITS_PER_PIXEL) *
        		IL.ilGetInteger(IL.IL_IMAGE_DEPTH) *
        		IL.ilGetInteger(IL.IL_IMAGE_WIDTH) * 
        		IL.ilGetInteger(IL.IL_IMAGE_HEIGHT)
        );

You mean IL_IMAGE_BYTES_PER_PIXEL

WHOOPS!
I'm an idiot. Sorry.

baegsi

#6
January 26, 2005, 20:01:22
Thanks, that's a better solution of course  :)
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