Question

I’m trying to draw a textured quad in XNA using the sample code from MSDN http://msdn.microsoft.com/en-us/library/bb464051.aspx

but instead of drawing it on XY plane i’m drawing it in XZ plane

I initialize that quad with this
this.quad = new Quad(Vector3.Zero, Vector3.Up, Vector3.Backward, 1, 1);

I’ve tried almost every combination of Normal and Left vector, no matter where the quad is drawn, the quad is completely black.

what am i doing wrong here? is the texture’s information lost when i’m passing it around? am i mapping the texture positions wrong?

ps: Texture, lighting are enabled.

public class Quad
{
    public VertexPositionNormalTexture[] Vertices;
    public Vector3 Origin;
    public Vector3 Up;
    public Vector3 Normal;
    public Vector3 Left;
    public Vector3 UpperLeft;
    public Vector3 UpperRight;
    public Vector3 LowerLeft;
    public Vector3 LowerRight;
    public int[] Indexes;


    public Quad(Vector3 origin, Vector3 normal, Vector3 up,
             float width, float height)
    {
            this.Vertices = new VertexPositionNormalTexture[4];
            this.Indexes = new int[6];
            this.Origin = origin;
            this.Normal = normal;
            this.Up = up;

            // Calculate the quad corners
            this.Left = Vector3.Cross(normal, this.Up);
            Vector3 uppercenter = (this.Up * height / 2) + origin;
            this.UpperLeft = uppercenter + (this.Left * width / 2);
            this.UpperRight = uppercenter - (this.Left * width / 2);
            this.LowerLeft = this.UpperLeft - (this.Up * height);
            this.LowerRight = this.UpperRight - (this.Up * height);

            this.FillVertices();
    }

    private void FillVertices()
    {
            Vector2 textureUpperLeft = new Vector2(0.0f, 0.0f);
            Vector2 textureUpperRight = new Vector2(1.0f, 0.0f);
            Vector2 textureLowerLeft = new Vector2(0.0f, 1.0f);
            Vector2 textureLowerRight = new Vector2(1.0f, 1.0f);

            for (int i = 0; i < this.Vertices.Length; i++)
            {
                    this.Vertices[i].Normal = this.Normal;
            }

            this.Vertices[0].Position = this.LowerLeft;
            this.Vertices[0].TextureCoordinate = textureLowerLeft;
            this.Vertices[1].Position = this.UpperLeft;
            this.Vertices[1].TextureCoordinate = textureUpperLeft;
            this.Vertices[2].Position = this.LowerRight;
            this.Vertices[2].TextureCoordinate = textureLowerRight;
            this.Vertices[3].Position = this.UpperRight;
            this.Vertices[3].TextureCoordinate = textureUpperRight;

            this.Indexes[0] = 0;
            this.Indexes[1] = 1;
            this.Indexes[2] = 2;
            this.Indexes[3] = 2;
            this.Indexes[4] = 1;
            this.Indexes[5] = 3;
    }
}

my draw method:

        graphicsDevice.BlendState = BlendState.AlphaBlend;

        Effect.World = Matrix.Identity;
        Effect.View = Camera.View;
        Effect.Projection = Camera.Projection;
        Effect.TextureEnabled = true;
        Effect.Texture = OilTexture;

        Effect.EnableDefaultLighting();
        Effect.PreferPerPixelLighting = true;


        foreach (EffectPass pass in oilEffect.CurrentTechnique.Passes)
        {
            pass.Apply();

            graphicsDevice.DrawUserIndexedPrimitives<VertexPositionNormalTexture>
                    (PrimitiveType.TriangleList,
                    Vertices,
                    0,
                    4,
                    Indexes,
                    0,
                    2);
        }

–i solved my problem. something went wrong when i was passing the texture2d across 3 places, now i’m drawing it from the main draw and the texture shows up fine now.

Answer 1

There are lots of reasons the quad could be black, here are a few things I like to do to debug:

• Turn off lightning and set on vert color to ensure the orientation of the quad is as I expected.
• User a sample texture, if possible, to ensure texture data is valid (I get a lot of issues with different versions of pipelines failing
  to load textures because the formats wasn’t what I expected. DDS has
  sub formats that can be tricky if you are making your own data)
• Check if the texture is visible with lightning off
• Once you flip lightning on you want to make sure you have lightning values set for all the vertices
• Try turning up the ambient value of your system to full

If none of this works look closely at the area where you are passing the vertex lightning values, the vertex normal values, and the lighting down to the hardware.