Processing output nothing using gouraud shading - glsl

Question

sorry, I am a new on opengl es and processing
below processing and shaders output only background
PShader Gouraud,Phong;
rocket = loadShape("rocket.obj");
rocket.setFill(color(800, 0, 0));
Gouraud= loadShader("gouraudfragment.glsl","gouraudvertex.glsl");
Phong= loadShader("phongfragment.glsl","phongvertex.glsl");
background(0);
pushMatrix();
shader(Gouraud);
translate(130,height/2.0);
rotateY(rc);
rotateX(0.4);
noStroke();
fill(#800080);
box(100);
rc+=(0.02+speedCube);
rc*=dirCube;
popMatrix();
pushMatrix();
shader(Gouraud);
translate(width/2, height/2 + 100, -200);
rotateZ(PI);
rotateY(rr);
shape(rocket,100,100);
rr +=( 0.02+speedRocket);
rr*=dirRocket;
popMatrix();
vertex shader
varying vec3 N;
varying vec3 v;
varying vec4 diffuse;
varying vec4 spec;
attribute vec4 position;
attribute vec3 normal;
uniform mat4 modelview;
uniform mat4 projectionMatrix;
uniform mat3 normalMatrix;
uniform vec4 lightPosition;
uniform vec3 lightAmbient;
uniform vec3 lightDiffuse;
uniform vec3 lightSpecular;
uniform float SpecularPower;
void main()
{
vec4 diffuse;
vec4 spec;
vec4 ambient;
v = vec3(modelview * position);
N = normalize(normalMatrix * normal);
gl_Position = projectionMatrix * position;
vec3 L = normalize(lightPosition.xyz - v);
vec3 E = normalize(-v);
vec3 R = normalize(reflect(-L,N));
ambient = vec4(lightAmbient,100.0);
diffuse = vec4(clamp( lightDiffuse * max(dot(N,L), 0.0) , 0.0, 1.0 ) ,100.0);
spec = vec4(clamp (lightSpecular * pow(max(dot(R,E),0.0),0.3*SpecularPower) , 0.0, 1.0 ),100.0);
color = ambient + diffuse + spec;
}
fragment shader
void main()
{
gl_FragColor = color;
}
please help!
before apply gouraud shading
after apply gouraud shading
The prcessing load the obj and the draw a cube and apply a gouraud shader, but after that only backgroud are shown, the obj loaded and cube is gone. nothing shown!

Answer 1

the shader doesn't even compile and link. The vertex shader has 1 varying output (color), so the framgent shader needs the input varying vec4 color;.
varying vec4 color;
When you set the clip space position, then the vertex coordinate has to be transformed by the model view and projection matrix:
gl_Position = projectionMatrix * modelview * position;
The types specifications of v and N are missing and the types of ambient, diffuse and spec are vec4 rather than vec3.
Vertex shader:
attribute vec4 position;
attribute vec3 normal;
varying vec4 color;
uniform mat4 modelview;
uniform mat4 projectionMatrix;
uniform mat3 normalMatrix;
uniform vec4 lightPosition;
uniform vec3 lightAmbient;
uniform vec3 lightDiffuse;
uniform vec3 lightSpecular;
uniform float SpecularPower;
void main()
{
vec3 v = vec3(modelview * position);
vec3 N = normalize(normalMatrix * normal);
gl_Position = projectionMatrix * modelview * position;
vec3 L = normalize(lightPosition.xyz - v);
vec3 E = normalize(-v);
vec3 R = normalize(reflect(-L,N));
vec4 ambient = vec4(lightAmbient,100.0);
vec4 diffuse = vec4(clamp( lightDiffuse * max(dot(N,L), 0.0) , 0.0, 1.0 ) ,100.0);
vec4 spec = vec4(clamp (lightSpecular * pow(max(dot(R,E),0.0),0.3*SpecularPower) , 0.0, 1.0 ),100.0);
color = ambient + diffuse + spec;
}
Fragment shader:
varying vec4 color;
void main()
{
gl_FragColor = color;
}
Of course you have to set at least an ambient light source ambientLight().
You can use a directionalLight(), pointLight() or spotLight(), too.
But note, your shader can handle 1 light source only. More the 1 light source would gain
OpenGL error 1282 at top endDraw(): invalid operation
If you want to use more than 1 light source then you would have to use uniform arrays int the vertex shader for lightPosition, lightAmbient, lightDiffuse, and lightSpecular. See Types of shaders in Processing(https://processing.org/tutorials/pshader/)