/*

     File: ASCSlideDelegateRendering.m

 Abstract: Explains what scene delegate rendering is and shows an example.

  Version: 1.1

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#import "ASCPresentationViewController.h"

#import "ASCSlideTextManager.h"

#import "ASCSlide.h"

#import "Utils.h"

#import "GLUtils.h"

// OpenGL attribute locations

NS_ENUM(GLuint, ASCAttrib) {

    ASC_QUAD_ATTRIB_POS,

    ASC_QUAD_ATTRIB_UV

};

// A structure used to represent a vertex

typedef struct {

    GLfloat position[4]; // position

    GLfloat uv0[3];      // texture coordinates + vertex index (stored in the last component)

} ASCVertexUV;

@interface ASCSlideDelegateRendering : ASCSlide <SCNSceneRendererDelegate>

@end

@implementation ASCSlideDelegateRendering {

    // OpenGL-related ivars

    GLuint _quadVAO;

    GLuint _quadVBO;

    GLuint _program;

    GLuint _timeLocation;

    GLuint _factorLocation;

    GLuint _resolutionLocation;

    // Other ivars

    GLfloat _fadeFactor;

    GLfloat _fadeFactorDelta;

    CFAbsoluteTime _startTime;

    CGSize _viewport;

}

- (NSUInteger)numberOfSteps {

    return 3;

}

- (void)setupSlideWithPresentationViewController:(ASCPresentationViewController *)presentationViewController {

    // Set the slide's title and subtitle and add some text

    self.textManager.title = @"Extending Scene Kit with OpenGL";

    self.textManager.subtitle = @"Scene delegate rendering";

    [self.textManager addBullet:@"Custom GL code, free of constraints" atLevel:0];

    [self.textManager addBullet:@"Before and/or after scene rendering" atLevel:0];

    [self.textManager addBullet:@"Works with SCNView, SCNLayer and SCNRenderer" atLevel:0];

    // Create a VBO to render a quad

    [self createQuadGeometryInContext:presentationViewController.view.openGLContext];

    // Create the program and retrieve the uniform locations

    ASCAttribLocation attrib[] = {

        {ASC_QUAD_ATTRIB_POS, "position"},

        {ASC_QUAD_ATTRIB_UV, "texcoord0"},

        {0, 0}

    };

    _program = ASCCreateProgramWithNameAndAttributeLocations(@"SceneDelegate", attrib);

    _timeLocation = glGetUniformLocation(_program, "time");

    _factorLocation = glGetUniformLocation(_program, "factor");

    _resolutionLocation = glGetUniformLocation( _program, "resolution");

    // Initialize time and cache the viewport

    NSSize frameSize = [presentationViewController.view convertSizeToBacking:presentationViewController.view.frame.size];

    _viewport = NSSizeToCGSize(frameSize);

    _startTime = CFAbsoluteTimeGetCurrent();

}

- (void)presentStepIndex:(NSUInteger)index withPresentionViewController:(ASCPresentationViewController *)presentationViewController {

    switch (index) {

        case 1:

            _fadeFactor = 0; // tunnel is not visible

            _fadeFactorDelta = 0.05; // fade in

            // Set self as the scene renderer's delegate and make the view redraw for ever

            presentationViewController.view.delegate = self;

            presentationViewController.view.playing = YES;

            presentationViewController.view.loops = YES;

            break;

        case 2:

            _fadeFactorDelta *= -1; // fade out

            break;

    }

}

- (void)willOrderOutWithPresentionViewController:(ASCPresentationViewController *)presentationViewController {

    presentationViewController.view.delegate = nil;

    presentationViewController.view.playing = NO;

}

// Create a VBO used to render a quad

- (void)createQuadGeometryInContext:(NSOpenGLContext *)context {

    [context makeCurrentContext];

    glGenVertexArraysAPPLE(1, &_quadVAO);

    glBindVertexArrayAPPLE(_quadVAO);

    glGenBuffers(1, &_quadVBO);

    glBindBuffer(GL_ARRAY_BUFFER, _quadVBO);

    ASCVertexUV vertices[] = {

        {{-1.f, 1.f, 0.f, 1.f}, {0.f, 1.f, 0.f}}, // TL

        {{ 1.f, 1.f, 0.f, 1.f}, {1.f, 1.f, 1.f}}, // TR

        {{-1.f,-1.f, 0.f, 1.f}, {0.f, 0.f, 2.f}}, // BL

        {{-1.f,-1.f, 0.f, 1.f}, {0.f, 0.f, 2.f}}, // BL

        {{ 1.f, 1.f, 0.f, 1.f}, {1.f, 1.f, 1.f}}, // TR

        {{ 1.f,-1.f, 0.f, 1.f}, {1.f, 0.f, 3.f}}, // BR

    };

    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    glVertexAttribPointer(ASC_QUAD_ATTRIB_POS, 4, GL_FLOAT, GL_FALSE, sizeof(ASCVertexUV), (void *)offsetof(ASCVertexUV, position));

    glEnableVertexAttribArray(ASC_QUAD_ATTRIB_POS);

    glVertexAttribPointer(ASC_QUAD_ATTRIB_UV, 3, GL_FLOAT, GL_TRUE, sizeof(ASCVertexUV), (void *)offsetof(ASCVertexUV, uv0));

    glEnableVertexAttribArray(ASC_QUAD_ATTRIB_UV);

    glBindVertexArrayAPPLE(0);

}

// Invoked by Scene Kit before rendering the scene. When this is invoked, Scene Kit has already installed the viewport and cleared the background.

- (void)renderer:(id <SCNSceneRenderer>)aRenderer willRenderScene:(SCNScene *)scene atTime:(NSTimeInterval)time {

    // Disable what Scene Kit enables by default (and restore upon leaving)

    glDisable(GL_CULL_FACE);

    glDisable(GL_DEPTH_TEST);

    // Draw the procedural background

    glBindVertexArrayAPPLE(_quadVAO);

    glUseProgram(_program);

    glUniform1f(_timeLocation, CFAbsoluteTimeGetCurrent() - _startTime);

    glUniform1f(_factorLocation, _fadeFactor);

    glUniform2f(_resolutionLocation, _viewport.width, _viewport.height);

    glDrawArrays(GL_TRIANGLES, 0, 6);

    glBindVertexArrayAPPLE(0);

    // Restore Scene Kit default states

    glEnable(GL_DEPTH_TEST);

    // Update the fade factor

    _fadeFactor = MAX(0, MIN(1, _fadeFactor + _fadeFactorDelta));

}

@end