CODEWITHSUNDEEP
xcode4ios-simulatoropengl-es-2.0
CrazyESbeginner
CrazyESbeginner

Reputation: 31

OpenGL ES 2.0 specifying normals for vertex shader

I am not able to get the right shading on all the faces of the cube I drew. I get a smooth transition from one of the face to another face which does not show the edge properly.

One a different face (where I get the desired edge), I get the shading such that it shows the two triangles which make up that face. I believe the problem is with the normals I am specifying. I am attaching my vertex and normal matrix and my vertex and fragment shader code. vertex and normal matrix are same.

I guess the problem is with the normals but I have tried almost everything with them but the effect does not change.

//normal matrix and vertex matrix are same

static const float normals[]=

    {
         //v0,v1,v2,v3,
         //v4,v5,v6,v7
        0.5,0.5,0.5, -0.5,0.5,0.5, -0.5,-0.5,0.5, 0.5,-0.5,0.5, 

        0.5,0.5,-0.5, -0.5,0.5,-0.5, -0.5,-0.5,-0.5, 0.5,-0.5,-0.5 

    };

//vertex shader

attribute vec4 color;
attribute vec4 position; 

attribute vec4 normal;

uniform mat4 u_mvpMatrix;
uniform vec4 lightDirection;
uniform vec4 lightDiffuseColor;
uniform float translate;

varying vec4 frontColor;



//varying vec4 colorVarying;



void main()

{

   vec4 normalizedNormal = normalize(u_mvpMatrix* normal);
   vec4 normalizedLightDirection = normalize(lightDirection);

   float nDotL = max(dot(normalizedNormal, normalizedLightDirection), 0.0);


   frontColor =  color * nDotL * lightDiffuseColor;


  gl_Position = u_mvpMatrix * position;


}

//fragment shader

varying lowp vec4 frontColor;

void main()
{


        gl_FragColor = frontColor;


}

Please help? Thanks in advance !!

Upvotes: 3

Views: 3211

Answers (1)

rotoglup
rotoglup

Reputation: 5283

Your problem is not related to your normal matrix, it is related to your input normals.

From what I read, you provide 8 normals, one for each vertex, meaning that you provide pre-averaged normals ; there is no way your vertex shader can un-average them.

To have proper discontinuities in your lighting, you need discontinuous normals : for each quad, you have 4 vertices, each with a normal matching the quad normal. So you end up with 6x4 = 24 normals (so as many vertices).

You may want to take a look at this for more detailed explanation : http://www.songho.ca/opengl/gl_vertexarray.html

Upvotes: 2

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