/*

    File: BoingRenderer.m

Abstract: 

This class handles the rendering of a Boing ball using Core Profile.

 Version: 1.2

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*/

#import "BoingRenderer.h"

#import <GLKit/GLKit.h>

typedef struct

{

    float x;

    float y;

    float z;

    float nx;

    float ny;

    float nz;

    float r;

    float g;

    float b;

    float a;

} Vertex;

static float lightDir[3]    = { 0.8, 4.0, 1.0 };

static float ambient[4]     = { 0.35, 0.35, 0.35, 0.35 };

static float diffuse[4]     = { 1.0-0.35, 1.0-0.35, 1.0-0.35, 1.0 };

static float specular[4]    = { 0.8, 0.8, 0.8, 1.0 };

static float shininess      = 10.0;

@interface BoingRenderer()

{    

    // Cribbed from BoingX

    float angle;

    float angleDelta;

    float r;

    float xPos, yPos;

    float xVelocity, yVelocity;

    float scaleFactor;

    GLKVector3 lightDirNormalized;

    GLKMatrix4 projectionMatrix;

    GLuint vboId, vaoId;

}

@end

@implementation BoingRenderer

-(void)generateBoingData

{

    int x;

    int index = 0;

    float v1x, v1y, v1z;

    float v2x, v2y, v2z;

    float d;

    int theta, phi;

    float theta0, theta1;

    float phi0, phi1;

    Vertex quad[4];

    Vertex *boingData = malloc(8 * 16 * 6 * sizeof(Vertex));

    float delta = M_PI / 8.0f;

    // 8 vertical segments

    for(theta = 0; theta < 8; theta++)

    {

        theta0 = theta*delta;

        theta1 = (theta+1)*delta;

        // 16 horizontal segments

        for(phi = 0; phi < 16; phi++)

        {

            phi0 = phi*delta;

            phi1 = (phi+1)*delta;

            // Generate 4 points per quad

            quad[0].x = r * sin(theta0)*cos(phi0);

            quad[0].y = r * cos(theta0);

            quad[0].z = r * sin(theta0)*sin(phi0);

            quad[1].x = r * sin(theta0)*cos(phi1);

            quad[1].y = r * cos(theta0);

            quad[1].z = r * sin(theta0)*sin(phi1);

            quad[2].x = r * sin(theta1)*cos(phi1);

            quad[2].y = r * cos(theta1);

            quad[2].z = r * sin(theta1)*sin(phi1);

            quad[3].x = r * sin(theta1)*cos(phi0);

            quad[3].y = r * cos(theta1);

            quad[3].z = r * sin(theta1)*sin(phi0);

            // Generate normal

            if(theta >= 4)

            {

                v1x = quad[1].x - quad[0].x;

                v1y = quad[1].y - quad[0].y;

                v1z = quad[1].z - quad[0].z;

                v2x = quad[3].x - quad[0].x;

                v2y = quad[3].y - quad[0].y;

                v2z = quad[3].z - quad[0].z;

            }

            else

            {

                v1x = quad[0].x - quad[3].x;

                v1y = quad[0].y - quad[3].y;

                v1z = quad[0].z - quad[3].z;

                v2x = quad[2].x - quad[3].x;

                v2y = quad[2].y - quad[3].y;

                v2z = quad[2].z - quad[3].z;

            }

            quad[0].nx = (v1y * v2z) - (v2y * v1z);

            quad[0].ny = (v1z * v2x) - (v2z * v1x);

            quad[0].nz = (v1x * v2y) - (v2x * v1y);

            d = 1.0f/sqrt(quad[0].nx*quad[0].nx +

                          quad[0].ny*quad[0].ny +

                          quad[0].nz*quad[0].nz);

            quad[0].nx *= d;

            quad[0].ny *= d;

            quad[0].nz *= d;

            // Generate color

            if((theta ^ phi) & 1)

            {

                quad[0].r = 1.0f;

                quad[0].g = 1.0f;

                quad[0].b = 1.0f;

                quad[0].a = 1.0f;

            }

            else

            {

                quad[0].r = 1.0f;

                quad[0].g = 0.0f;

                quad[0].b = 0.0f;

                quad[0].a = 1.0f;

            }

            // Replicate vertex info

            for(x = 1; x < 4; x++)

            {

                quad[x].nx = quad[0].nx;

                quad[x].ny = quad[0].ny;

                quad[x].nz = quad[0].nz;

                quad[x].r = quad[0].r;

                quad[x].g = quad[0].g;

                quad[x].b = quad[0].b;

                quad[x].a = quad[0].a;

            }

            // OpenGL draws triangles under the hood. Core Profile officially drops support

            // of the GL_QUADS mode in the glDrawArrays/Elements calls.

            // Store vertices as in two consisting triangles

            boingData[index++] = quad[0];

            boingData[index++] = quad[1];

            boingData[index++] = quad[2];

            boingData[index++] = quad[2];

            boingData[index++] = quad[3];

            boingData[index++] = quad[0];

        }

    }

    // Create a VAO (vertex array object).

    glGenVertexArrays(1, &vaoId);

    glBindVertexArray(vaoId);

    // Create a VBO (vertex buffer object) to hold our data.

    glGenBuffers(1, &vboId);

    glBindBuffer(GL_ARRAY_BUFFER, vboId);

    glBufferData(GL_ARRAY_BUFFER, 8 * 16 * 6 * sizeof(Vertex), boingData, GL_STATIC_DRAW);

    // positions

    glVertexAttribPointer(ATTRIB_VERTEX, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLubyte *)(uintptr_t)offsetof(Vertex,x));

    // colors

    glVertexAttribPointer(ATTRIB_COLOR, 4, GL_FLOAT, GL_TRUE, sizeof(Vertex), (GLubyte *)(uintptr_t)offsetof(Vertex,r));

    // normals

    glVertexAttribPointer(ATTRIB_NORMAL, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLubyte *)(uintptr_t)offsetof(Vertex,nx));

    // At this point the VAO is set up with three vertex attributes referencing the same buffer object.

    free(boingData);

}

- (void)initShaders:(programInfo_t *)program

{

    for (int i = 0; i < NUM_PROGRAMS; i++)

    {

        // set constant uniforms

        glUseProgram(program[i].id);

        if (i == PROGRAM_LIGHTING)

        {

            // Set up lighting stuff used by the shaders

            glUniform3fv(program[i].uniform[UNIFORM_LIGHTDIR], 1, lightDirNormalized.v);

            glUniform4fv(program[i].uniform[UNIFORM_AMBIENT], 1, ambient);

            glUniform4fv(program[i].uniform[UNIFORM_DIFFUSE], 1, diffuse);

            glUniform4fv(program[i].uniform[UNIFORM_SPECULAR], 1, specular);

            glUniform1f(program[i].uniform[UNIFORM_SHININESS], shininess);

        }

        else if (i == PROGRAM_PASSTHRU)

        {

            glUniform4f(program[i].uniform[UNIFORM_CONSTANT_COLOR], 0.0f,0.0f,0.0f,0.4f);

        }

    }

}

- (instancetype)init

{

    if (self = [super init])

    {

        angleDelta = -0.05f;

        scaleFactor = 1.6;

        r = scaleFactor * 48.0f;

        xVelocity = 1.5f;

        yVelocity = 0.0f;

        xPos = r*2.0f;

        yPos = r*5.0f;

        // normalize light dir

        lightDirNormalized = GLKVector3Normalize(GLKVector3MakeWithArray(lightDir));

        projectionMatrix = GLKMatrix4Identity;

        [self generateBoingData];

    }

    return self;

}

- (void)makeOrthographicForWidth:(CGFloat)width height:(CGFloat)height

{

    projectionMatrix = GLKMatrix4MakeOrtho(0, width, 0, height, 0.0f, 2000.0);

}

- (void)update

{

    // Do "physics" stuff

    yVelocity -= 0.05f;

    xPos += xVelocity*scaleFactor;

    yPos += yVelocity*scaleFactor;

    if(xPos < (r+10.0f))

    {

        xPos = r+10.f;

        xVelocity = -xVelocity;

        angleDelta = -angleDelta;

    }

    else if(xPos > (310*scaleFactor-r))

    {

        xPos = 310*scaleFactor-r;

        xVelocity = -xVelocity;

        angleDelta = -angleDelta;

    }

    if(yPos < r)

    {

        yPos = r;

        yVelocity = -yVelocity;

    }

    angle += angleDelta;

    if(angle < 0.0f)

        angle += 360.0f;

    else if(angle > 360.0f)

        angle -= 360.0f;

}

- (void)render:(programInfo_t *)program

{

    GLKMatrix4 modelViewMatrix, MVPMatrix, modelViewMatrixIT;

    GLKMatrix3 normalMatrix;

    glBindVertexArray(vaoId);

    // Draw "shadow"

    glUseProgram(program[PROGRAM_PASSTHRU].id);

    glEnable(GL_CULL_FACE);

    glDisable(GL_DEPTH_TEST);

    glDepthMask(GL_FALSE);

    glEnable(GL_BLEND);

    glBlendFunc(GL_SRC_ALPHA_SATURATE, GL_ONE_MINUS_SRC_ALPHA);

    // Make the "shadow" move around a bit. This is not a real shadow projection.

    GLKVector3 pos = GLKVector3Normalize(GLKVector3Make(xPos, yPos, -100.0f));                                     

    modelViewMatrix = GLKMatrix4MakeTranslation(xPos + (pos.v[0]-lightDirNormalized.v[0])*20.0,

                                                yPos + (pos.v[1]-lightDirNormalized.v[1])*10.0,

                                                -800.0f);

    modelViewMatrix = GLKMatrix4Rotate(modelViewMatrix, -16.0f, 0.0f, 0.0f, 1.0f);

    modelViewMatrix = GLKMatrix4Rotate(modelViewMatrix, angle, 0.0f, 1.0f, 0.0f);

    modelViewMatrix = GLKMatrix4Scale(modelViewMatrix, 1.05f, 1.05f, 1.05f);

    MVPMatrix = GLKMatrix4Multiply(projectionMatrix, modelViewMatrix);

    glUniformMatrix4fv(program[PROGRAM_PASSTHRU].uniform[UNIFORM_MVP], 1, GL_FALSE, MVPMatrix.m);

    glEnableVertexAttribArray(ATTRIB_VERTEX);

    glEnableVertexAttribArray(ATTRIB_COLOR);

    glDrawArrays(GL_TRIANGLES, 0, 8*16*6);

    // Draw real Boing

    glUseProgram(program[PROGRAM_LIGHTING].id);

    glEnable(GL_DEPTH_TEST);

    glDepthMask(GL_TRUE);

    glDepthFunc(GL_LESS);

    glDisable(GL_BLEND);

    // ModelView

    modelViewMatrix = GLKMatrix4MakeTranslation(xPos, yPos, -100.0f);

    modelViewMatrix = GLKMatrix4Rotate(modelViewMatrix, -16.0f, 0.0f, 0.0f, 1.0f);

    modelViewMatrix = GLKMatrix4Rotate(modelViewMatrix, angle, 0.0f, 1.0f, 0.0f);

    glUniformMatrix4fv(program[PROGRAM_LIGHTING].uniform[UNIFORM_MODELVIEW], 1, GL_FALSE, modelViewMatrix.m);

    // MVP

    MVPMatrix = GLKMatrix4Multiply(projectionMatrix, modelViewMatrix);

    glUniformMatrix4fv(program[PROGRAM_LIGHTING].uniform[UNIFORM_MVP], 1, GL_FALSE, MVPMatrix.m);

    // ModelViewIT (normal matrix)

    bool success;

    modelViewMatrixIT = GLKMatrix4InvertAndTranspose(modelViewMatrix, &success);

    if (success) {

        normalMatrix = GLKMatrix4GetMatrix3(modelViewMatrixIT);

        glUniformMatrix3fv(program[PROGRAM_LIGHTING].uniform[UNIFORM_MODELVIEWIT], 1, GL_FALSE, normalMatrix.m);

    }

    glEnableVertexAttribArray(ATTRIB_NORMAL);

    glDrawArrays(GL_TRIANGLES, 0, 8*16*6);

    glDisableVertexAttribArray(ATTRIB_VERTEX);

    glDisableVertexAttribArray(ATTRIB_COLOR);

    glDisableVertexAttribArray(ATTRIB_NORMAL);

    glUseProgram(0);

}

- (void)dealloc

{

    if (vboId) {

        glDeleteBuffers(1, &vboId);

        vboId = 0;

    }

    if (vaoId) {

        glDeleteVertexArrays(1, &vaoId);

        vaoId = 0;

    }

    [super dealloc];

}

@end