current community

your communities

more stack exchange communities

Stack Exchange
tour help
Take the 2-minute tour ×
Game Development Stack Exchange is a question and answer site for professional and independent game developers. It's 100% free, no registration required.
up vote 0 down vote favorite

I am trying to adjust the following code to render a quad on a 2D texture at a specific location and specific size. Currently this code will render a fullscreen quad, which makes sense since the POSITION semantic is being set to the fullscreen size.

My issue, is that I don't know how to adjust the POSITION semantics in the declaration below to use the specified location and size of a texture.

private short[] indexData = new short[] { 0, 1, 2, 2, 3, 0 };

private VertexPositionTexture[] CreateTriangles(Vector2 location, 
                                                float width, float height)
{

    // how do I get these values, and where do I set them below?
    float topleft = ??;
    float topRight = ??;
    float bottomLeft = ??;
    float bottomRight = ??;

    VertexPositionTexture[] vertices = new VertexPositionTexture[]
    {
        new VertexPositionTexture(new Vector3(1f, -1f, 0f), 
                                  new Vector2(1, 1)),
        new VertexPositionTexture(new Vector3(-1f, -1f, 0), 
                                  new Vector2(0, 1)),
        new VertexPositionTexture(new Vector3(-1f, 1f, 0), 
                                  new Vector2(0, 0)),
        new VertexPositionTexture(new Vector3(1f, 1f, 0), 
                                  new Vector2(1, 0)) 
    };

    return vertices;
}

All I'm trying to do is render a quad overtop of a texture at a specific location. If I use the code as-is with my texture is will stretch the texture to the entire size of the screen (again, makes sense because of how the POSITION semantic is being set).

share|improve this question

2 Answers 2

up vote 0 down vote

In the code here : 

new VertexPositionTexture(new Vector3(1f, -1f, 0f), 
                                  new Vector2(1, 1)),
        new VertexPositionTexture(new Vector3(-1f, -1f, 0), 
                                  new Vector2(0, 1)),
        new VertexPositionTexture(new Vector3(-1f, 1f, 0), 
                                  new Vector2(0, 0)),
        new VertexPositionTexture(new Vector3(1f, 1f, 0), 
                                  new Vector2(1, 0))

You try to adjust the Quad Size, by defining 4 points. Depends on whether you try to define them in clockwise or counterclock wise, you can set the positions , topleft, tobRight, BottomLeft, BottomRight instead of those 4 points.

share|improve this answer
    
Thanks, I know I needed to change those points (that's what I was asking). I just didn't know how, but I figured it out anyway. –  test Nov 20 '14 at 19:33
up vote 0 down vote accepted

I figured it out. Hopefully this can help someone else.

private short[] indexData = new short[] { 0, 1, 2, 2, 3, 0 };

private VertexPositionTexture[] CreateTriangles(Vector2 location, 
                                                int width, int height)
{
    /* this is what the index data tells us
     * 
     * 2  ________________ 3
     *   |\               |
     *   |  \             |
     *   |    \           |
     *   |      \         |
     *   |        \       |
     *   |          \     |
     *   |            \   |
     *   |              \ |
     *   |________________|
     * 1                   0
     * 
     */

    float bbw = this.gfx.PresentationParameters.BackBufferWidth;
    float bbh = this.gfx.PresentationParameters.BackBufferHeight;

    float left = -(((bbw / 2f) - location.X) / (bbw / 2f));
    float top = (((bbh / 2f) - location.Y) / (bbh / 2f));
    float right = -(((bbw / 2f) - (location.X + width)) / (bbw / 2f));
    float bottom = (((bbh / 2f) - (location.Y + height)) / (bbh / 2f));

    // this is how the triangle points are specified
    VertexPositionTexture[] vertices = new VertexPositionTexture[]
    {

        // point 0
        new VertexPositionTexture(new Vector3(right, bottom, 0f), 
                                  new Vector2(1, 1)),

        // point 1
        new VertexPositionTexture(new Vector3(left, bottom, 0f), 
                                  new Vector2(0, 1)),

        // point 2
        new VertexPositionTexture(new Vector3(left, top, 0f), 
                                  new Vector2(0, 0)),

        // point 3
        new VertexPositionTexture(new Vector3(right, top, 0f), 
                                  new Vector2(1, 0)) 

    };

    return vertices;
}
share|improve this answer
    
Is this is an answer please mark it as answer. –  user52551 Feb 19 at 19:27

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.