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Thevenin

OpenGL 1D Texture to span 2D Quad

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In order to avoid "P=NP" style programming challenge (aka, box-sorting algorithm), I made my texture 1D (even though it should be 2D). Basically, I grab several Bitmaps, play around with the pixels until each are of long 1 pixel thin (contiguous) line, and then shove them all into a 1D Texture. In past, I do this (for when using 2D Texture):
cGL.glBegin(cGL.GL_QUADS);

cGL.glColor4ub(TheColor.MyR, TheColor.MyG, TheColor.MyB, TheColor.MyA);

cGL.glTexCoord2f(TheTextureX1, TheTextureY1);
cGL.glVertex2i(TheDstX, TheDstY);

cGL.glTexCoord2f(TheTextureX2, TheTextureY1);
cGL.glVertex2i(TheDstX + TheSrcWidth, TheDstY);

cGL.glTexCoord2f(TheTextureX2, TheTextureY2);
cGL.glVertex2i(TheDstX + TheSrcWidth, TheDstY + TheSrcHeight);

cGL.glTexCoord2f(TheTextureX1, TheTextureY2);
cGL.glVertex2i(TheDstX, TheDstY + TheSrcHeight);

cGL.glEnd();
cGL.sCheckOpenGLError();


But now I need to change that "glTexCoord2f" to "1f" (or 1d). And I'm not sure what values to put in it.

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It cannot be done in any sane way. If you want a 2D texture, what's wrong with a 2D texture?

I may be possible to achieve some kind of result if and only if the only thing you're drawing is a screen aligned quad whose size in pixel matches exactly that of the 2D sub-texture...

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Quote:
Original post by Brother Bob
It cannot be done in any sane way. If you want a 2D texture, what's wrong with a 2D texture?


It was Julian's recommendation on #gamedev two months ago that I use a 1D Texture to save myself from having to write a box-sorting algorithm for my hardware wrapper. Basically, my code allows the user to play with OpenGL as if it were GDI (aka, none of this power of 2 crap, or minimizing texture binds).

My code takes in any sized bitmap, and shoves it into VRAM (if the bitmap is larger than a texture, it will automatically make rendering it consider of multiple renders from different textured quads, and if the bitmap is small enough to fit onto an existing allocated texture (average case), it will simply shove it on it).

Because the user doesn't have to be concerned with how the textures are stored in VRAM, fragmentation (subtextures removed, and replaced with new ones) is very prone to occur. And by using a 1D texture, it becomes very easy to deal with.

Quote:
Original post by Brother Bob
I may be possible to achieve some kind of result if and only if the only thing you're drawing is a screen aligned quad whose size in pixel matches exactly that of the 2D sub-texture...


Yes, that holds. My wrapper cannot even do linear-filtering. A pixel on the texture will correspond to a pixel on the screen (or a natural integer power of 2 multiple; for instance, 1x 2x 4x 8x GL_NEAREST zooming) always.

What's your idea?

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Quote:
Original post by Thevenin
Yes, that holds. My wrapper cannot even do linear-filtering. A pixel on the texture will correspond to a pixel on the screen (or a natural integer power of 2 multiple; for instance, 1x 2x 4x 8x GL_NEAREST zooming) always.

What's your idea?

May be possible, but with 1x zoom only. I cannot see a solution with any other zoom at all. I had an initial idea though, but it failed because the necessary texture coordinates became non-planar and the interpolation failed.

The problem, really, is that you require two degrees of freedom in your interpolation, but you only have one interpolation factor. Concider this case as an example. You have a 2x2 texel 2D texture stuck in a 4 texel 1D texture, like this.

| A B |
2D = | | --> 1D = | A B C D |
| C D |

Sampling the texture between A and B is a matter of interpolating between A and B along the X-axis, which works in the 1D texture also. Sampling between A and C gives you B in the 1D texture though...

edit: Oh, and in case you wasn't aware of it, that "non-power of two only crap" was removed from the specification three and a half years ago.

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Alright, my solution is evidently "no go". Damn Julian and his (her?) misunderstanding of what it was I was trying to do! All the code I wrote this morning (for resolving when to shift around fragments in 1D) is useless now... [bawling]

Code Written This Morning

using System;
using System.Collections.Generic;
using System.Text;
using System.Drawing;
using System.IO;
using cMinimalDeps;

namespace FrostWindow
{
struct aVRAMSlot
{
public int MyIndex;
public int MyLength;
public cVRAMCylinder MyTexture;
public int MyFrequency; /* Number of times used in 100 frames. */

public aVRAMSlot(int TheIndex, int TheLength, cVRAMCylinder TheTexture)
{
this.MyIndex = TheIndex;
this.MyLength = TheLength;
this.MyTexture = TheTexture;
this.MyFrequency = 0;
}
}

internal class cVRAMCylinder
{
public aColor[] MyPixels = null;
public int MyTextureID = -1;

public cVRAMCylinder()
{
MyPixels = new aColor[cGL.MyTextureSize];
sLoad();
}
public void sLoad()
{
if (MyTextureID != -1)
throw new Exception("Texture is already loaded. Call sUnload() before sLoad()!");
MyTextureID = cGL.glGenerateTexture(MyPixels);
}
public void sUnload()
{
/* glDeleteTextures silently ignores 0's and names that do not
correspond to existing textures.
-- http://www.opengl.org/documentation/specs/man_pages/hardcopy/GL/html/gl/deletetextures.html
*/

cGL.glDeleteTexture(MyTextureID);
MyTextureID = -1;
}
}

public class cFrostTex : IDisposable
{
internal aVRAMSlot[] MyComposition = null;
public int MyWidth = 0;
public int MyHeight = 0;

public cFrostTex(int TheWidth, int TheHeight) : this(TheWidth, TheHeight, null) { }
public cFrostTex(int TheWidth, int TheHeight, aColor[] ThePixels)
{
if (TheWidth <= 0 || TheHeight <= 0)
throw new Exception("Width and Height must both be greater than 0.");

this.MyWidth = TheWidth;
this.MyHeight = TheHeight;
MyComposition = cVRAM.sNewTexture(TheWidth, TheHeight);

if (ThePixels != null)
{
for (int TheLoopX = 0; TheLoopX < MyWidth; TheLoopX++)
for (int TheLoopY = 0; TheLoopY < MyHeight; TheLoopY++)
sSetPixel(TheLoopX, TheLoopY, ThePixels[(TheLoopY * TheWidth) + TheLoopX]);
}

/* Write this to the VRAM. */
sRefresh();
}

public aColor sGetPixel(int TheX, int TheY)
{
int ThePixelAccessed = (MyWidth * TheY) + TheX;
int TheOffset = 0;

/* This code uses a loop and alot of reference lookups just to get a single pixel on system RAM. :/ */
for (int TheCylinderLoop = 0; TheCylinderLoop < MyComposition.Length; TheCylinderLoop++)
{
if (TheOffset + MyComposition[TheCylinderLoop].MyLength < ThePixelAccessed)
TheOffset += MyComposition[TheCylinderLoop].MyLength;
else
return MyComposition[TheCylinderLoop].MyTexture.MyPixels[ThePixelAccessed - TheOffset];
}

/* If we've gotten here, something terrible has happened. */
throw new Exception("Could not find requested pixel in texture.");
}

public void sDraw(int TheSrcX, int TheSrcY, int TheSrcWidth, int TheSrcHeight,
int TheDstX, int TheDstY, aRect TheClipping, aColor TheColor)
{


/* Ok, so basically, there may be mulitiple renders here, depending on how many cylinders were used. */
for (int TheLoop = 0; TheLoop < MyComposition.Length; TheLoop++)
{
/* Calculate the actual position of the*/
float TheTextureX1 = (float)TheSrcX / cGL.MyTextureSize;
float TheTextureY1 = (float)TheSrcY / cGL.MyTextureSize;

float TheTextureX2 = (float)(TheSrcX + TheSrcWidth) / cGL.MyTextureSize;
float TheTextureY2 = (float)(TheSrcY + TheSrcHeight) / cGL.MyTextureSize;



if (!TheTexture.MyOnVRAM) throw new Exception("Trying to render texture that isn't on VRAM.");
if (MyCurrentBoundTexture != TheTexture.MyTexture)
{
cGL.glBindTexture(cGL.GL_TEXTURE_1D, TheTexture.MyTexture);
MyCurrentBoundTexture = TheTexture.MyTexture;
}

cGL.glBegin(cGL.GL_QUADS);

cGL.glColor4ub(TheColor.MyR, TheColor.MyG, TheColor.MyB, TheColor.MyA);

cGL.glTexCoord2f(TheTextureX1, TheTextureY1);
cGL.glVertex2i(TheDstX, TheDstY);

cGL.glTexCoord2f(TheTextureX2, TheTextureY1);
cGL.glVertex2i(TheDstX + TheSrcWidth, TheDstY);

cGL.glTexCoord2f(TheTextureX2, TheTextureY2);
cGL.glVertex2i(TheDstX + TheSrcWidth, TheDstY + TheSrcHeight);

cGL.glTexCoord2f(TheTextureX1, TheTextureY2);
cGL.glVertex2i(TheDstX, TheDstY + TheSrcHeight);

cGL.glEnd();
cGL.sCheckOpenGLError();
}
}

public void sSetPixel(int TheX, int TheY, aColor TheColor)
{
cVRAM.sSetPixel(this, TheColor,TheX,TheY);
}
public void sRefresh()
{
cVRAM.sRefreshCylinders(this.MyComposition);
}

/* For debug support. */
public Bitmap sToBitmap()
{
/* Create a bitmap, and set pixel it. */
Bitmap TheBitmap = new Bitmap(cGL.MyTextureSize, cGL.MyTextureSize);
for (int TheLoopX = 0; TheLoopX < cGL.MyTextureSize; TheLoopX++)
for (int TheLoopY = 0; TheLoopY < cGL.MyTextureSize; TheLoopY++)
{
aColor TheColor = sGetPixel(TheLoopX, TheLoopY);
TheBitmap.SetPixel(TheLoopX, TheLoopY, Color.FromArgb(TheColor.MyA,
TheColor.MyR, TheColor.MyG, TheColor.MyB));
}
return TheBitmap;
}

void IDisposable.Dispose()
{
cVRAM.sDisposeTexture(this);
}
}

internal static class cVRAM
{
/* Graphics handling. */
public static int MyBlitCount = 0;
private static int MyCurrentBoundTexture = -1;

/* All of the VRAM cartridges are 1D, and are listed here. The Cylinder also contains RAM backup of their pixel data. */
static List<cVRAMCylinder> MyCylinders = new List<cVRAMCylinder>();

/* As we pull cFrostTexs out of RAM, we are going to end up with fragmentations. */
static List<aVRAMSlot> MyFragments = new List<aVRAMSlot>();

public static aVRAMSlot[] sNewTexture(int TheWidth, int TheHeight)
{
int ThePixelsRemaining = TheWidth * TheHeight;
List<aVRAMSlot> TheReturn = new List<aVRAMSlot>();

while (ThePixelsRemaining != 0)
{

/* Take the place of any fragments first! */
for (int TheLoop = 0; TheLoop < MyFragments.Count; TheLoop++)
{
aVRAMSlot TheSlot = MyFragments[TheLoop];

/* If we need the entire slot, then take it. */
if (TheSlot.MyLength <= ThePixelsRemaining)
{
TheReturn.Add(TheSlot);
MyFragments.Remove(TheSlot);
ThePixelsRemaining -= TheSlot.MyLength;
}
/* Else if we only need a little bit of it. */
else if (ThePixelsRemaining != 0)
{
MyFragments.Remove(TheSlot);

/* Build the remaining slot, and add it. */
aVRAMSlot TheRemainingSlot = new aVRAMSlot();
TheRemainingSlot.MyIndex = TheSlot.MyIndex + ThePixelsRemaining;
TheRemainingSlot.MyLength = TheSlot.MyLength - ThePixelsRemaining;
TheRemainingSlot.MyTexture = TheSlot.MyTexture;
MyFragments.Add(TheRemainingSlot);

/* Add what we took, to the return. */
aVRAMSlot TheWhatWeUsed = new aVRAMSlot();
TheWhatWeUsed.MyIndex = TheSlot.MyIndex;
TheWhatWeUsed.MyLength = ThePixelsRemaining;
TheWhatWeUsed.MyTexture = TheSlot.MyTexture;
TheReturn.Add(TheWhatWeUsed);
}
}

/* If after the fragments have been used, there still isn't enough room for the texture,
* build a new cylinder, and subsequently another (huge) fragment. */

if (ThePixelsRemaining != 0)
{
cVRAMCylinder TheNewCylinder = new cVRAMCylinder();
MyCylinders.Add(TheNewCylinder);
MyFragments.Add(new aVRAMSlot(0, cGL.MyTextureSize, TheNewCylinder));
}
}
return TheReturn.ToArray();
}

internal static void sSetPixel(cFrostTex TheTexture, aColor ThePixel, int TheX, int TheY)
{
int ThePixelAccessed = (TheTexture.MyWidth * TheY) + TheX;
int TheOffset = 0;

/* This code uses a loop and alot of reference lookups just to place a single pixel on system RAM. :/ */
for(int TheCylinderLoop = 0; TheCylinderLoop<TheTexture.MyComposition.Length; TheCylinderLoop++)
{
if(TheOffset + TheTexture.MyComposition[TheCylinderLoop].MyLength < ThePixelAccessed)
TheOffset += TheTexture.MyComposition[TheCylinderLoop].MyLength;
else
{
TheTexture.MyComposition[TheCylinderLoop].MyTexture.MyPixels[ThePixelAccessed - TheOffset] = ThePixel;
return;
}
}

/* If we've gotten here, we could not find the pixel to write to. */
throw new Exception("Could not find the pixel we were suppose to write to.");
}

/* To handle reallocating the surfaces, lest they become lost or disposed. */
internal static void sLoadResources()
{
for (int TheLoop = 0; TheLoop < MyCylinders.Count; TheLoop++)
MyCylinders[TheLoop].sLoad();
}
internal static void sUnloadResources()
{
for (int TheLoop = 0; TheLoop < MyCylinders.Count; TheLoop++)
MyCylinders[TheLoop].sUnload();
}
internal static void sDisposeTexture(cFrostTex TheTexture)
{
/* All of the segments that correspond to this texture become loose fragments! */
for (int TheLoop = 0; TheLoop < TheTexture.MyComposition.Length; TheLoop++)
MyFragments.Add(TheTexture.MyComposition[TheLoop]);
}

/* To handling applying the changes made to textures in cylinders. */
internal static void sRefreshCylinders(aVRAMSlot[] TheBands)
{
for (int TheLoop = 0; TheLoop < TheBands.Length; TheLoop++)
{
aColor[] TheCopiedPixels = new aColor[TheBands[TheLoop].MyLength];
Array.Copy(TheBands[TheLoop].MyTexture.MyPixels, TheBands[TheLoop].MyIndex, TheCopiedPixels,0, TheBands[TheLoop].MyLength);
cGL.glBindTexture(cGL.GL_TEXTURE_1D, TheBands[TheLoop].MyTexture.MyTextureID);
cGL.glTexSubImage1D(cGL.GL_TEXTURE_1D, 0, TheBands[TheLoop].MyIndex, TheBands[TheLoop].MyLength,
cGL.GL_RGBA, cGL.GL_UNSIGNED_BYTE, TheCopiedPixels);
}
}

internal static void sOptimize()
{
/* There was a barber and his wife... */
throw new Exception("sOptimize() not implemented yet.");
}
}
}



... oh well, it was fun. And I learned a valuable lesson about optimistically adhering to advice given by those whose gender is otherwise disputed.

[Edited by - Thevenin on February 20, 2008 1:13:36 PM]

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