/*
dd_redleft_pattern.cpp 
5 April 2021

Based on the shader code given in the Arnold doc "Creating a Shader".
https://docs.arnoldrenderer.com/display/AFMUG/Creating+a+shader#CreatingaShader-1.1.1InstallingaC++Compiler
*/

#include <ai.h>
#include <cstring>
#include <math.h>

AI_SHADER_NODE_EXPORT_METHODS(SampleMethods);
AtRGB mix(AtRGB a, AtRGB b, float alpha){
	return a*(1-alpha) +b *alpha;
	}	

namespace {
    enum paramIndex { k_pat_color, k_base_color, k_offset, k_direction, k_blur, k_urepeats, k_vrepeats, k_ushift, k_vshift};
    };

static const char* menu_items[] = { "U", "V","Radial", NULL };

node_parameters {
    AiParameterRGB("patternColor", 0.7f, 0, 0);
    AiParameterRGB("baseColor", 0.7f, 0.7f, 0);

    AiParameterFlt("offset", 0.5);
    AiParameterEnum("direction", 1, menu_items);
	AiParameterFlt("blur", 0);
	
	AiParameterFlt("u_repeats", 1); // u_repeats becomes "U Repeats"
	AiParameterFlt("v_repeats", 1);
	AiParameterFlt("u_shift", 0);
	AiParameterFlt("v_shift", 0);
    }

shader_evaluate {
    AtRGB base = AiShaderEvalParamRGB(k_pat_color);
    AtRGB pat = AiShaderEvalParamRGB(k_base_color);

    float offset = AiShaderEvalParamFlt(k_offset);
    int  dir = AiShaderEvalParamEnum(k_direction);
	float blur = AiShaderEvalParamFlt(k_blur);
	
	float u_reps = AiShaderEvalParamFlt(k_urepeats);
	float v_reps = AiShaderEvalParamFlt(k_vrepeats);
	float u_shift = AiShaderEvalParamFlt(k_ushift);
	float v_shift = AiShaderEvalParamFlt(k_vshift);
	
	float blend;
	// how all repeating patterns work...
	float u_copy = fmod(sg->u * u_reps,1);
	float v_copy = fmod(sg->v * v_reps,1);
	
	//row 
	int row = floor(sg->v * v_reps);
	bool rowIsEven = (row%2 ? 1:0); 
	if(rowIsEven)
		 u_copy = fmod((sg->u+u_shift) * u_reps,1);
	
	//column 	
	int col = floor(sg->u * u_reps);
	bool colIsEven = (col%2? 1:0);
	if(colIsEven)
		v_copy = fmod((sg->v + v_shift) * v_reps,1);
	
	//main
    if(dir == 0)
        //sg->out.RGB() = (sg->u >= offset) ? pat : base;
		blend = AiSmoothStep(offset - blur, offset, u_copy);//sg->u);
    else if(dir==1)
        //sg->out.RGB() = (sg->v >= offset) ? pat : base;
		blend = AiSmoothStep(offset - blur, offset, v_copy);//sg->v);
	else
		{
		// find the distance of the current shading point(u,v)
		// to the center of the uv space(0.5,0.5) and then 
		// test to the offset value.
		float a = v_copy - 0.5;//sg->v -0.5;
		float b = 0.5- u_copy;// 0.5- sg->u;
		float hyp = sqrt(a*a+b*b);
		blend = AiSmoothStep(offset - blur, offset, hyp);
	
		}
		sg->out.RGB() = mix(base,pat,blend);
    }

node_loader {
    if (i > 0)
        return false;
    node->methods        = SampleMethods;
    node->output_type    = AI_TYPE_RGB;
	node->name           = "dd_redleft_pattern";
    node->node_type      = AI_NODE_SHADER;
    strcpy(node->version, AI_VERSION);
    return true;
    }

// The remaining macros can be left "empty"
node_initialize { }
node_update { }
node_finish { }