Assignment 4

Helpful tools

Shaders.h
Shaders.cpp
Plane.obj
terrainDiffuse.png
terrainHeight.png
terrainNormal.png

In this project I hope to show you how to work the tesillation shaders, the tessillation controler and the tessillation evaluator.
From the "Helpful tools panel, download and replace Shaders.h and Shaders.cpp files in your project with these new ones.
Draw a plane on the screen. Then tessallate it (just draw it in wire mode). Use the Camera to get a better view.

Extra: Can you control the level of tessallation from the keyboard?

Ok, I felt a little bad about just making you look at my tessilation shader code and you all panicing to try to copy it. My intent was to show what was going in these two new added stages, not just to ask you to be Xerox machines. In truth, the process of tessillation is rather rigid, there is very little modifications you can make. In that light, let me go back over the four new shaders.

Tessillation Vert:

layout(location = 0) in vec4 vVertex;
layout(location = 1) in vec3 vNormal;
layout(location = 2) in vec2 uvCoord;

uniform mat4 projectionMatrix;
uniform mat4 viewMatrix;
uniform mat4 modelMatrix;

out vec2 uvCoordFromVert;
out vec3 normalFromVert;
void main() {
    uvCoordFromVert = uvCoord;
    normalFromVert = vNormal;
    gl_Position =  vVertex;
}

Tessillation control:

layout(vertices = 3) out;

///uniform float tessLevelInner;
///uniform float tessLevelOuter;

in vec2 uvCoordFromVert[];
in vec3 normalFromVert[];

out vec2 uvCoordFromCtrl[];
out vec3 normalFromCtrl[];
void main() {
    /// Pass through input vertices to tessellation evaluation stage
    gl_out[gl_InvocationID].gl_Position =  gl_in[gl_InvocationID].gl_Position;
    uvCoordFromCtrl[gl_InvocationID] = uvCoordFromVert[gl_InvocationID];
    normalFromCtrl[gl_InvocationID] = normalFromVert[gl_InvocationID];

   float tesslevel = 1.0;
    /// Set tessellation levels
    if (gl_InvocationID == 0) {
        gl_TessLevelInner[0] = tesslevel;

        gl_TessLevelOuter[0] = tesslevel;
        gl_TessLevelOuter[1] = tesslevel;
        gl_TessLevelOuter[2] = tesslevel;

    }
}

Tessillation evaluator:

layout (triangles, equal_spacing, ccw) in;

uniform mat4 projectionMatrix;
uniform mat4 viewMatrix;
uniform mat4 modelMatrix;
uniform sampler2D textureData;

in vec2 uvCoordFromCtrl[];
in vec3 normalFromCtrl[];

out vec2 uvCoordFromEval;
out vec3 normalFromEval;

vec2 interpolateVec2(vec2 v0, vec2 v1, vec2 v2) {
    return gl_TessCoord.x * v0 + gl_TessCoord.y * v1 + gl_TessCoord.z * v2;
}

vec3 interpolateVec3(vec3 v0, vec3 v1, vec3 v2) {
    return  gl_TessCoord.x * v0 + gl_TessCoord.y * v1 + gl_TessCoord.z * v2;
}

vec4 interpolateVec4(vec4 v0, vec4 v1, vec4 v2) {
    return  gl_TessCoord.x * v0 + gl_TessCoord.y * v1 + gl_TessCoord.z * v2;
}

void main() {
   
    uvCoordFromEval = interpolateVec2(uvCoordFromCtrl[0], uvCoordFromCtrl[1], uvCoordFromCtrl[2]);
    normalFromEval =  interpolateVec3(normalFromCtrl[0], normalFromCtrl[1], normalFromCtrl[2]);
    /// Interpolate position across the triangle
    vec4 position = interpolateVec4(gl_in[0].gl_Position, gl_in[1].gl_Position, gl_in[2].gl_Position);

    ///vec4 height = vec4(texture(textureData,uvCoordFromEval));
    ///position.z =  height.r;
    gl_Position =  projectionMatrix * viewMatrix * modelMatrix * position ;
}

Tessillation frag:

in vec2 uvCoordFromEval;
in vec3 normalFromEval;
out vec4 fragColor;
uniform sampler2D textureData;
void main() {
    ///fragColor = texture(textureData,uvCoordFromEval);
    fragColor = vec4(1.0,1.0,1.0,1.0);
}