/*

     File: ASCSlideCustomProgram.m

 Abstract: Shows how Scene Kit allows one to use custom GLSL programs.

  Version: 1.1

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 */

#import "ASCPresentationViewController.h"

#import "ASCSlideTextManager.h"

#import "ASCSlide.h"

#import "Utils.h"

#import <OpenGL/gl3.h>

#import <GLKit/GLKMath.h>

@interface ASCSlideCustomProgram : ASCSlide

@end

@implementation ASCSlideCustomProgram {

    SCNNode *_torusNode;

}

- (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 = @"Material custom program";

    [self.textManager addBullet:@"Custom GLSL code per material" atLevel:0];

    [self.textManager addBullet:@"Overrides Scene Kit’s rendering" atLevel:0];

    [self.textManager addBullet:@"Geometry attributes are provided" atLevel:0];

    [self.textManager addBullet:@"Transform uniforms are also provided" atLevel:0];

    // Add a torus and animate it

    _torusNode = [self.groundNode asc_addChildNodeNamed:@"torus" fromSceneNamed:@"torus" withScale:10];

    _torusNode.position = SCNVector3Make(8, 8, 4);

    _torusNode.name = @"object";

    CABasicAnimation *rotationAnimation = [CABasicAnimation animationWithKeyPath:@"rotation"];

    rotationAnimation.duration = 10.0;

    rotationAnimation.repeatCount = FLT_MAX;

    rotationAnimation.toValue = [NSValue valueWithSCNVector4:SCNVector4Make(0, 1, 0, M_PI * 2)];

    [_torusNode addAnimation:rotationAnimation forKey:nil];

}

// The following method will create a new SCNGeometry instance by duplicating its vertices in 3 instances and assigning each one of them texture coordinates representing the 3 corners of a triangle, containing entirely a quad of canonical (0..1) coordinates.

// This is usually done by generating the four vertices of the quad but with a triangle we have less 1 less vertex per quad to transform (at the expense of lost fragment bandwith).

//

// v0 (-1.0, -1.0) ---------  v1 (3.0, -1.0)

//                 |===   /

//                 |===  /

//                 |=== /

//                 |   /

//                 |  /

//                 | /

//                 |/

//                 v2 (-1.0, 3.0)

//

// The geometry is created by interleaving vertices data, allowing a more efficient vertex pulling by the graphics card.

typedef struct {

    GLKVector3 morphPositionSrc;

    GLKVector3 morphPositionDst;

    GLKVector2 texCoord;

} ASCMorphVertex;

- (SCNGeometry *)spriteGeometryWithRadius:(CGFloat)radius sourceGeometry:(SCNGeometry *)geometry {

    SCNGeometrySource *vertexSource = [geometry geometrySourcesForSemantic:SCNGeometrySourceSemanticVertex][0];

    NSInteger vectorCount = vertexSource.vectorCount;

    NSInteger vertexCount = vectorCount * 3;

    UInt8 *srcVertices = (UInt8 *)vertexSource.data.bytes + vertexSource.dataOffset;

    NSInteger srcStride = vertexSource.dataStride;

    ASCMorphVertex *dstVertices = malloc(sizeof(ASCMorphVertex) * vertexCount);

    for (NSUInteger i = 0; i < vectorCount; ++i) {

        ASCMorphVertex *v0 = &dstVertices[i * 3];

        ASCMorphVertex *v1 = &dstVertices[i * 3 + 1];

        ASCMorphVertex *v2 = &dstVertices[i * 3 + 2];

        GLKVector3 position = *(GLKVector3 *)(srcVertices + srcStride * i);

        // source position

        v0->morphPositionSrc = position;

        v1->morphPositionSrc = position;

        v2->morphPositionSrc = position;

        // compute the destination position, a random point on a sphere of specified radius

        position = GLKVector3Make((2.f * (float)rand() / RAND_MAX - 1.f), (2.f * (float)rand() / RAND_MAX - 1.f), (2.f * (float)rand() / RAND_MAX - 1.f));

        position = GLKVector3MultiplyScalar(GLKVector3Normalize(position), radius);

        v0->morphPositionDst = position;

        v1->morphPositionDst = position;

        v2->morphPositionDst = position;

        // texture coordinates

        v0->texCoord = GLKVector2Make(-1.f, -1.f);

        v1->texCoord = GLKVector2Make( 3.f, -1.f);

        v2->texCoord = GLKVector2Make(-1.f,  3.f);

    }

    // Create three geometry sources : position, normal and texture coordinates

    NSData *interleavedVertexData = [NSData dataWithBytesNoCopy:dstVertices length:vertexCount * sizeof(ASCMorphVertex) freeWhenDone:YES];

    SCNGeometrySource *positionSource = [SCNGeometrySource geometrySourceWithData:interleavedVertexData

                                                                         semantic:SCNGeometrySourceSemanticVertex

                                                                      vectorCount:vectorCount

                                                                  floatComponents:YES

                                                              componentsPerVector:3

                                                                bytesPerComponent:sizeof(float)

                                                                       dataOffset:offsetof(ASCMorphVertex, morphPositionSrc)

                                                                       dataStride:sizeof(ASCMorphVertex)];

    SCNGeometrySource *normalSource = [SCNGeometrySource geometrySourceWithData:interleavedVertexData

                                                                       semantic:SCNGeometrySourceSemanticNormal

                                                                    vectorCount:vectorCount

                                                                floatComponents:YES

                                                            componentsPerVector:3

                                                              bytesPerComponent:sizeof(float)

                                                                     dataOffset:offsetof(ASCMorphVertex, morphPositionDst)

                                                                     dataStride:sizeof(ASCMorphVertex)];

    SCNGeometrySource *texCoordSource = [SCNGeometrySource geometrySourceWithData:interleavedVertexData

                                                                         semantic:SCNGeometrySourceSemanticTexcoord

                                                                      vectorCount:vectorCount

                                                                  floatComponents:YES

                                                              componentsPerVector:2

                                                                bytesPerComponent:sizeof(float)

                                                                       dataOffset:offsetof(ASCMorphVertex, texCoord)

                                                                       dataStride:sizeof(ASCMorphVertex)];

    // Create the indices (each vertex is used only once per triangle)

    GLint *indices = (GLint *)malloc(sizeof(GLint) * vertexCount);

    for (GLint i = 0; i < vertexCount; ++i)

        indices[i] = i;

    NSData *indicesData = [NSData dataWithBytesNoCopy:indices length:vertexCount * sizeof(GLint) freeWhenDone:YES];

    // Create a geometry element from the indices

    SCNGeometryElement *elements = [SCNGeometryElement geometryElementWithData:indicesData

                                                                 primitiveType:SCNGeometryPrimitiveTypeTriangles

                                                                primitiveCount:vertexCount / 3

                                                                 bytesPerIndex:4];

    // Create the geometry from the three geometry sources and the geometry element

    SCNGeometry *newGeometry = [SCNGeometry geometryWithSources:@[positionSource, normalSource, texCoordSource]

                                                       elements:@[elements]];

    // Use the same materials

    newGeometry.materials = geometry.materials;

    return newGeometry;

}

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

    switch (index) {

        case 1:

        {

            // Create the supporting geometry and replace the existing one

            _torusNode = [self.groundNode childNodeWithName:@"object" recursively:YES];

            _torusNode.geometry = [self spriteGeometryWithRadius:8. sourceGeometry:_torusNode.geometry];

            // Create a custom program using a vertex and a fragment shader

            NSURL *vertexShaderURL = [[NSBundle mainBundle] URLForResource:@"CustomProgram" withExtension:@"vsh"];

            NSURL *fragmentShaderURL = [[NSBundle mainBundle] URLForResource:@"CustomProgram" withExtension:@"fsh"];

            SCNProgram *program = [SCNProgram program];

            program.vertexShader = [NSString stringWithContentsOfURL:vertexShaderURL encoding:NSASCIIStringEncoding error:NULL];

            program.fragmentShader = [NSString stringWithContentsOfURL:fragmentShaderURL encoding:NSASCIIStringEncoding error:NULL];

            // Bind geometry source semantics to the vertex shader attributes

            [program setSemantic:SCNGeometrySourceSemanticVertex forSymbol:@"a_srcPos" options:nil];

            [program setSemantic:SCNGeometrySourceSemanticNormal forSymbol:@"a_dstPos" options:nil];

            [program setSemantic:SCNGeometrySourceSemanticTexcoord forSymbol:@"a_texcoord" options:nil];

            // Bind the uniforms that can benefit from "automatic" values, computed and assigned by Scene Kit at each frame

            [program setSemantic:SCNModelViewTransform forSymbol:@"u_mv" options:nil];

            [program setSemantic:SCNProjectionTransform forSymbol:@"u_proj" options:nil];

            // Other uniforms will be set using binding blocks

            static float morphFactor = 0.0;

            morphFactor = -M_PI_2;

            [_torusNode.geometry.firstMaterial handleBindingOfSymbol:@"factor" usingBlock:^(unsigned int programID, unsigned int location, SCNNode *renderedNode, SCNRenderer *renderer) {

                // animate the "factor" uniform to morph from the original object to the sphere

                morphFactor += 0.01;

                glUniform1f(location, sin(morphFactor) * 0.5 + 0.5);

            }];

            CFTimeInterval startTime = CFAbsoluteTimeGetCurrent();

            [_torusNode.geometry.firstMaterial handleBindingOfSymbol:@"time" usingBlock:^(unsigned int programID, unsigned int location, SCNNode *renderedNode, SCNRenderer *renderer) {

                // animate the "time" uniform to make the particles spin

                glUniform1f(location, CFAbsoluteTimeGetCurrent() - startTime);

            }];

            // Use our custom program and make the material not to interact at all with the depth buffer (to provide an additive effect)

            _torusNode.geometry.firstMaterial.program = program;

            _torusNode.geometry.firstMaterial.writesToDepthBuffer = NO;

            _torusNode.geometry.firstMaterial.readsFromDepthBuffer = NO;

            _torusNode.renderingOrder = 100; // as the geometry doesn't interact with the depth buffer, the node needs to be rendered last

            break;

        }

        case 2:

            // Display the related sample code

            [self.textManager fadeOutTextOfType:ASCTextTypeBullet];

            [self.textManager addEmptyLine];

            [self.textManager addCode:

             @"[aMaterial #handleBindingOfSymbol:#@\"myUniform\" \n"

             @"                      #usingBlock:# \n"

             @"       ^(unsigned int programID, \n"

             @"         unsigned int location, \n"

             @"         SCNNode *node, \n"

             @"         SCNRenderer *renderer) { \n"

             @"    glUniform1f(location, aValue); \n"

             @"}];"];

            [self.textManager flipInTextOfType:ASCTextTypeCode];

            break;

    }

}

@end