Simple Lena Quad POD

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    Hi again –

    Just running through all the PVRShaman demos to get acquainted. I have the latest SDK on Mac and they all run except for the quad.pod (with the ubiquitous Lena!). Just a dark screen. I simplified the frag to the most basic vertex/shader possible and still no go. So I looked into the Object Data for Plane 01 and inspected Vertices and UVs (should be all that’s relevant right?) A few questions:

    – should it run out of box?

    – The vertices seem to be in a different order. The vertex code suggests an xzy order

                  Â gl_Position = vec4(inVertex.x, inVertex.z, 0, 1.0);


    – About the UV0 setting. How does the utility “glDraw”? In strips or fans or other? How is that controller.

    I would like to setup a very simple quad for either strip or fan ordering -1,-1 1,-1 1,1 -1,1 with a standard UV map of 0,0 1,0 1,1 0,1. At the moment, all I need is a simple quad scene to test some ES2 shaders for image post-processing. No fancy 3D. I am new to the POD and its object format.

    Any suggestions and clarifications to the previous questions are appreciated.

    Thanks in advance. Patrice

    Update: created a simple quad object and the scene renders her just fine. Still not sure what is happening in ripple and refact. At least I experiment with my shaders there.

    pkouame2010-11-18 19:39:51



    Ok – I’m developing a nasty habit of answering my own questions…(while waiting ahem…)

    1 – Anyway the vshader isn’t transforming the position correctly. The MVPMatrix dropped out as a factor for gl_position (typo?) As such nothing will show.

    2- The vertex vector being passed to gl_position is swapping Y for Z.

    I believe the vshader should look something like this (if I understand the intent…)


         NAME VertShader


              attribute highp      vec4 inVertex;

              attribute mediump vec2 inTexCoord;


              uniform highp   mat4 MVPMatrix;

              varying mediump vec2 TexCoord;


              varying highp vec4 Position;


              void main()


                   gl_Position = MVPMatrix * vec4( , 1.0);

                   Position = gl_Position;

                   TexCoord = inTexCoord;




    3 – Lastly, the MVPMatrix needs to be declared in the EFFECT tag. And TextCoord was being flipped vertically (why?)

    Again, I am assuming the intent was to blur central parts of her face following the mouse position. I may be wrong of course.

    I think Lena may have suffered from some neglect over time 😉 She IS getting a little old in the tooth…


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