Home/ Questions/Q 6101255
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-23T13:28:44+00:00

Texturing headache… I can’t understand where i go wrong here. My problem is that

  • 0

Texturing headache…

I can’t understand where i go wrong here. My problem is that the texture is not aligned. The image on the left is the OpenGl textured quad, and the right is the original. Notice how the columns are offset in the textured quad.

Mis-aligned texture

I don’t know if i am not loading the texture properly, or make a mistake during uploading it to videomemory, or simply use the wrong texCoords…

The image is a bmp (R8 G8 B8 A8) and the mistake lies somewhere in here:

(Loading of bitmap and uploading of texture)

        Bitmap fontBmp = new Bitmap("font2.bmp");
        MemoryStream ms = new MemoryStream();

        fontBmp.Save(ms, ImageFormat.Bmp);
        int imageWidth = fontBmp.Width;
        int imageHeight = fontBmp.Height;
        byte[] fontBytes = ms.GetBuffer();
        fontBmp.Dispose();
        ms.Dispose();

        Gl.glBindTexture(Gl.GL_TEXTURE_2D, (int)TexId.font);
        Gl.glPixelStorei(Gl.GL_UNPACK_ALIGNMENT, 1);
        Gl.glTexParameteri(Gl.GL_TEXTURE_2D, Gl.GL_TEXTURE_WRAP_S, Gl.GL_CLAMP_TO_EDGE);
        Gl.glTexParameteri(Gl.GL_TEXTURE_2D, Gl.GL_TEXTURE_WRAP_T, Gl.GL_CLAMP_TO_EDGE);
        Gl.glTexParameteri(Gl.GL_TEXTURE_2D, Gl.GL_TEXTURE_MAG_FILTER, Gl.GL_NEAREST);
        Gl.glTexParameteri(Gl.GL_TEXTURE_2D, Gl.GL_TEXTURE_MIN_FILTER, Gl.GL_NEAREST);
        Gl.glTexEnvf(Gl.GL_TEXTURE_ENV, Gl.GL_TEXTURE_ENV_MODE, Gl.GL_MODULATE); // Try GL_DECAL...
        Gl.glTexImage2D(Gl.GL_TEXTURE_2D, 0, Gl.GL_RGBA, imageWidth, imageHeight, 0, Gl.GL_RGBA, Gl.GL_UNSIGNED_BYTE, fontBytes);

(The quad…)

        Gl.glTexCoord2f(0f + (0.5f / 128f), (127f / 128f) + (0.5f / 128f));
        Gl.glVertex2i(50, 50);

        Gl.glTexCoord2f(0f + (0.5f / 128f), 0f + (0.5f / 128f)); 
        Gl.glVertex2i(50, this.Height - 50);

        Gl.glTexCoord2f((127f / 128f) + (0.5f / 128f), 0f + (0.5f / 128f)); 
        Gl.glVertex2i(this.Width - 50, this.Height - 50);

        Gl.glTexCoord2f((127f / 128f) + (0.5f / 128f), (127f / 128f) + (0.5f / 128f)); 
        Gl.glVertex2i(this.Width - 50, 50);

Does anyone spot anything causing this?

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    The problem is NOT your texture coordinates.

    The problem is that you’re loading the texture wrong. You’re forgetting to remove the bitmap header, so all the real data is shifted over, and the end of each line is shifted onto the beginning of the next line.

    Texture wrapping would wrap pixels from the right back onto the same line, but the out-of-place region is shifted down one row. Texture wrapping also wouldn’t occur with the “clamp to edge” mode you’ve enabled.

    • 0