Re: [HOpenGL] Texture Mapping??

Hi again Hector, On 11/07/10 16:30, Hector Guilarte wrote:

Hello Claude,

Sorry for the delay - some things came up.

My problem is everywhere hahaha. I haven't been able to do anything with textures, but those steps do sound like the way to go. Maybe if you could explain them a little bit more I'll do it, or maybe with the examples you mentioned I'll get it myself.

Ok, here is a dump of relevant portions of my code. They all require (and other imports are noted above the snippets): import Graphics.UI.GLUT

When you say 'load' is the hardest: In all the tutorials or codes I've seen, I haven't been able to find any function which has that kind of signature, but I really have no idea on how to do such function myself :s. I really thought maybe OpenGL provided some functions to do it...

The main problem is the variety of different image formats - most are compressed which means using corresponding libraries to decompress them - and even for uncompressed images they usually have a header with useful information such as width, height, channels. -- For a file containing raw RGBA pixels (1 byte per channel) -- hardcoded to 1024x1024x4 widthXheightXchannels): -- this actually does load + upload in one function import Control.Monad(when) import System.Exit(exitFailure) import System.IO(withBinaryFile, IOMode(ReadMode), openBinaryFile, hGetBuf) import Foreign.Marshal.Alloc(allocaBytes) loadTexture :: FilePath -> IO TextureObject loadTexture f = do withBinaryFile f ReadMode $ \h -> do let bytes = 1024 * 1024 * 4 allocaBytes bytes $ \pixels -> do bytes' <- hGetBuf h pixels bytes when (bytes' /= bytes) exitFailure [tex] <- genObjectNames 1 texture Texture2D $= Enabled textureBinding Texture2D $= Just tex build2DMipmaps Texture2D RGBA' 1024 1024 (PixelData RGBA UnsignedByte pixels) textureFilter Texture2D $= ((Linear', Just Linear'), Linear') textureWrapMode Texture2D S $= (Repeated, ClampToEdge) textureWrapMode Texture2D T $= (Repeated, ClampToEdge) textureBinding Texture2D $= Nothing texture Texture2D $= Disabled return tex -- To convert SVG via PNG via PPM/PGM to a suitable raw format I use -- a simple bash script (I called it "svg2rgba.sh") -- warning: this assumes that the SVG has width = height = 1024 pixels -- the magic numbers are 3 * width * height and 1 * width * height -- given "foo.svg", convert it to "foo.rgba" by running: -- ./svg2rgba.sh foo #!/bin/bash SVGFILE="${1}.svg" PNGFILE="${1}.png" PPMFILE="${1}.ppm" PGMFILE="${1}.pgm" RGBFILE="${1}.rgb" AFILE="${1}.a" RGBAFILE="${1}.rgba" rsvg "${SVGFILE}" "${PNGFILE}" pngtopnm "${PNGFILE}" > "${PPMFILE}" pngtopnm -alpha "${PNGFILE}" > "${PGMFILE}" tail -c 3145728 "${PPMFILE}" > "${RGBFILE}" tail -c 1048576 "${PGMFILE}" > "${AFILE}" ./interleave31 "${RGBFILE}" "${AFILE}" > "${RGBAFILE}" rm -f "${PNGFILE}" "${PPMFILE}" "${PGMFILE}" "${RGBFILE}" "${AFILE}" -- to interleave the raw data I use this C code -- again hardcoded to width = height = 1024 -- error checking and speed leaves much to be desired -- save as "interleave31.c" -- compile with: gcc -o interleave31 interleave31.c #include int main(int argc, char **argv) { if (argc != 3) { return 1; } FILE *in3 = fopen(argv[1], "rb"); if (in3) { FILE *in1 = fopen(argv[2], "rb"); if (in1) { for (int i = 0; i < 1024*1024; ++i) { putchar(getc(in3)); putchar(getc(in3)); putchar(getc(in3)); putchar(getc(in1)); } fclose(in1); } else { return 1; } fclose(in3); } else { return 1; } return 0; }

upload :: .... -- upload to the Graphics Card? I've used OpenGL in C++ and adding a texture is so easy, Probably I did all 3 steps you mention, but I never really worried about them, I just did it without paying attention on what was happening underneath.

import Foreign.Ptr(Ptr()) import Foreign.Marshal.Alloc(mallocBytes) data Image = Image{ iWidth, iHeight, iChannels :: Int, iBuffer :: Ptr () } image :: Int -> Int -> Int -> IO Image image w h c | w > 0 && h > 0 && c > 0 = do b <- mallocBytes $ w * h * c return Image{ iWidth = w, iHeight = h, iChannels = c, iBuffer = b } | otherwise = error $ "Image.image: " ++ show [w,h,c] upload :: Image -> IO TextureObject upload i | iChannels i == 4 = do [tex] <- genObjectNames 1 texture Texture2D $= Enabled textureBinding Texture2D $= Just tex build2DMipmaps Texture2D RGBA' (fromIntegral $ iWidth i) (fromIntegral $ iHeight i) (PixelData RGBA UnsignedByte (iBuffer i)) textureFilter Texture2D $= ((Linear', Just Linear'), Linear') textureWrapMode Texture2D S $= (Repeated, ClampToEdge) textureWrapMode Texture2D T $= (Repeated, ClampToEdge) textureBinding Texture2D $= Nothing texture Texture2D $= Disabled return tex | otherwise = error $ "Image.upload: " ++ show (iChannels i) -- Should be simple to adapt the above to handle channels /= 4

draw :: ... This does sounds like what I used to do in C++ and it's what I was hoping to find in Haskell...

data Quad = Quad{ quadX, quadY, quadR :: GLdouble, quadT :: TextureObject } -- cannot rebind texture within renderPrimitive -- might be more efficient to use 1 large texture -- with subportions of that 1 texture for each quad drawQuad :: Quad -> IO () drawQuad Quad{ quadX = x0, quadY = y0, quadR = s, quadT = tex } = do let t x y = texCoord $ TexCoord2 (x :: GLdouble) (y :: GLdouble) v x y = vertex $ Vertex2 x y textureBinding Texture2D $= Just tex renderPrimitive Quads $ do color $ Color3 1 1 (1::GLdouble) t 0 1 >> v (x0 - s) (y0 + s) t 0 0 >> v (x0 - s) (y0 - s) t 1 0 >> v (x0 + s) (y0 - s) t 1 1 >> v (x0 + s) (y0 + s) drawQuads :: [Quad] -> IO () drawQuads qs = do blend $= Enabled blendFunc $= (SrcAlpha, OneMinusSrcAlpha) texture Texture2D $= Enabled mapM_ drawQuad qs textureBinding Texture2D $= Nothing texture Texture2D $= Disabled blend $= Disabled

Thank you,

Hoping this helps,

Hector Guilarte

Claude

On Sun, Jul 11, 2010 at 10:06 AM, Claude Heiland-Allen mailto:claudiusmaximus@goto10.org> wrote:

Hi Hector,

On 11/07/10 03:02, Hector Guilarte wrote: > I've been looking for a way to map a texture into a Quad primitive with > HOpenGL with no luck. [snip]

I'm having trouble understanding where your problem is.

There are three steps to texturing using an image file:

load :: FilePath -> IO Image -- read file to raw pixel buffer upload :: Image -> IO TextureObject -- upload to graphics card draw :: TextureObject -> IO () -- use the texture on something

where data Image = Image{ width, height, channels :: Int, pixels :: Ptr () }

Which step is problematic?

'load' is the hardest IMO, and doesn't have anything to do with OpenGL. 'upload' I would implement with 'build2DMipmaps' 'draw' is easy: bind the texture, add a 'texCoord' before each 'vertex'

I could provide some example code for 'upload' and 'draw' if you think it would help.

Claude -- http://claudiusmaximus.goto10.org

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