问题
I implemented a 3ds modelloader following this tutorial. Currently my program uses VAOs do display things. This worked so far for simple cubes and tiles. Textures were displaying correctly.
However, when I load the 3DS model into a VAO its a different sotry. The model looks correct concerning the vertices, but the texture is mirrored along the Y axis for some reason.
This is how i read the UV:
case 0x4140:
qty = reader.ReadUInt16(); // 2 bytes
UV[] texcoords = new UV[qty];
for (i = 0; i < qty; i++)
{
texcoords[i] = new UV
{
U = reader.ReadSingle(), // 4 bytes
V = reader.ReadSingle() // 4 bytes
};
}
tb = new TexCoordBuffer(texcoords);
And the UV:
[StructLayout(LayoutKind.Sequential)]
struct UV
{
public float U { get; set; }
public float V { get; set; }
}
Creating the Attribute:
GL.EnableVertexAttribArray(2);
texCoordBuffer.Bind();
GL.VertexAttribPointer(2, 2, VertexAttribPointerType.Float, false, Vector2.SizeInBytes, 0);
GL.BindAttribLocation(shaderHandle, 2, "in_texture");
How the Texture is "created":
GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapS, (int)TextureWrapMode.Repeat);
GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapT, (int)TextureWrapMode.Repeat);
GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)TextureMagFilter.Linear);
GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)TextureMinFilter.LinearMipmapNearest);
GL.TexEnv(TextureEnvTarget.TextureEnv, TextureEnvParameter.TextureEnvMode, (int)TextureEnvMode.Replace);
GL.TexImage2D(
TextureTarget.Texture2D,
0,
PixelInternalFormat.Rgba,
bmpData.Width,
bmpData.Height,
0,
PixelFormat.Bgra,
PixelType.UnsignedByte,
bmpData.Scan0);
GL.GenerateMipmap(GenerateMipmapTarget.Texture2D);
This is how it turns out: Example left, my version right:
回答1:
Yes you should flip V texture coordinate when importing model for OpenGL. UV maps in 3DS model and OpenGL are different. OpenGL texture coordinates should be (U; 1-V)
This can be fixed either in import model code or by selecting corresponding option for flipping UV in your 3D modelling software.
You can take a look at answer and comments to understand this behavior in this related question: https://stackoverflow.com/a/8621571/405681
来源:https://stackoverflow.com/questions/14156476/mapping-texture-on-3ds-vao-turns-out-mirrored