GLdc/GL/lighting.c

#include <stdio.h>
#include <string.h>

#include <dc/vec3f.h>
#include "private.h"

static GLfloat SCENE_AMBIENT [] = {0.2, 0.2, 0.2, 1.0};
static GLboolean VIEWER_IN_EYE_COORDINATES = GL_TRUE;
static GLenum COLOR_CONTROL = GL_SINGLE_COLOR;
static GLboolean TWO_SIDED_LIGHTING = GL_FALSE;

static LightSource LIGHTS[MAX_LIGHTS];
static Material MATERIAL;

void initLights() {
    static GLfloat ONE [] = {1.0f, 1.0f, 1.0f, 1.0f};
    static GLfloat ZERO [] = {0.0f, 0.0f, 0.0f, 1.0f};
    static GLfloat PARTIAL [] = {0.2f, 0.2f, 0.2f, 1.0f};
    static GLfloat MOSTLY [] = {0.8f, 0.8f, 0.8f, 1.0f};

    memcpy(MATERIAL.ambient, PARTIAL, sizeof(GLfloat) * 4);
    memcpy(MATERIAL.diffuse, MOSTLY, sizeof(GLfloat) * 4);
    memcpy(MATERIAL.specular, ZERO, sizeof(GLfloat) * 4);
    memcpy(MATERIAL.emissive, ZERO, sizeof(GLfloat) * 4);
    MATERIAL.exponent = 0.0f;

    GLubyte i;
    for(i = 0; i < MAX_LIGHTS; ++i) {
        memcpy(LIGHTS[i].ambient, ZERO, sizeof(GLfloat) * 4);
        memcpy(LIGHTS[i].diffuse, ONE, sizeof(GLfloat) * 4);
        memcpy(LIGHTS[i].specular, ONE, sizeof(GLfloat) * 4);

        if(i > 0) {
            memcpy(LIGHTS[i].diffuse, ZERO, sizeof(GLfloat) * 4);
            memcpy(LIGHTS[i].specular, ZERO, sizeof(GLfloat) * 4);
        }

        LIGHTS[i].position[0] = LIGHTS[i].position[1] = LIGHTS[i].position[3] = 0.0f;
        LIGHTS[i].position[2] = 1.0f;

        LIGHTS[i].spot_direction[0] = LIGHTS[i].spot_direction[1] = 0.0f;
        LIGHTS[i].spot_direction[2] = -1.0f;

        LIGHTS[i].spot_exponent = 0.0f;
        LIGHTS[i].spot_cutoff = 180.0f;

        LIGHTS[i].constant_attenuation = 1.0f;
        LIGHTS[i].linear_attenuation = 0.0f;
        LIGHTS[i].quadratic_attenuation = 0.0f;
    }
}

void APIENTRY glLightModelf(GLenum pname, const GLfloat param) {
    glLightModelfv(pname, &param);
}

void APIENTRY glLightModeli(GLenum pname, const GLint param) {
    glLightModeliv(pname, &param);
}

void APIENTRY glLightModelfv(GLenum pname, const GLfloat *params) {
    switch(pname) {
        case GL_LIGHT_MODEL_AMBIENT:
            memcpy(SCENE_AMBIENT, params, sizeof(GLfloat) * 4);
        break;
        case GL_LIGHT_MODEL_LOCAL_VIEWER:
            VIEWER_IN_EYE_COORDINATES = (*params) ? GL_TRUE : GL_FALSE;
        break;
    case GL_LIGHT_MODEL_TWO_SIDE:
        /* Not implemented */
    default:
        _glKosThrowError(GL_INVALID_ENUM, __func__);
        _glKosPrintError();
    }
}

void APIENTRY glLightModeliv(GLenum pname, const GLint* params) {
    switch(pname) {
        case GL_LIGHT_MODEL_COLOR_CONTROL:
            COLOR_CONTROL = *params;
        break;
        case GL_LIGHT_MODEL_LOCAL_VIEWER:
            VIEWER_IN_EYE_COORDINATES = (*params) ? GL_TRUE : GL_FALSE;
        break;
    default:
        _glKosThrowError(GL_INVALID_ENUM, __func__);
        _glKosPrintError();
    }
}

void APIENTRY glLightfv(GLenum light, GLenum pname, const GLfloat *params) {
    GLubyte idx = light & 0xF;

    if(idx >= MAX_LIGHTS) {
        return;
    }

    switch(pname) {
        case GL_AMBIENT:
            memcpy(LIGHTS[idx].ambient, params, sizeof(GLfloat) * 4);
        break;
        case GL_DIFFUSE:
            memcpy(LIGHTS[idx].diffuse, params, sizeof(GLfloat) * 4);
        break;
        case GL_SPECULAR:
            memcpy(LIGHTS[idx].specular, params, sizeof(GLfloat) * 4);
        break;
        case GL_POSITION:
            memcpy(LIGHTS[idx].position, params, sizeof(GLfloat) * 4);
        break;
        case GL_CONSTANT_ATTENUATION:
        case GL_LINEAR_ATTENUATION:
        case GL_QUADRATIC_ATTENUATION:
        case GL_SPOT_CUTOFF:
        case GL_SPOT_DIRECTION:
        case GL_SPOT_EXPONENT:
            glLightf(light, pname, *params);
    default:
        _glKosThrowError(GL_INVALID_ENUM, __func__);
        _glKosPrintError();
    }
}

void APIENTRY glLightf(GLenum light, GLenum pname, GLfloat param) {
    GLubyte idx = light & 0xF;

    if(idx >= MAX_LIGHTS) {
        return;
    }

    switch(pname) {
        case GL_CONSTANT_ATTENUATION:
            LIGHTS[idx].constant_attenuation = param;
        break;
        case GL_LINEAR_ATTENUATION:
            LIGHTS[idx].linear_attenuation = param;
        break;
        case GL_QUADRATIC_ATTENUATION:
            LIGHTS[idx].quadratic_attenuation = param;
        break;
        case GL_SPOT_EXPONENT:
        case GL_SPOT_CUTOFF:
    default:
        _glKosThrowError(GL_INVALID_ENUM, __func__);
        _glKosPrintError();
    }
}

void APIENTRY glMaterialf(GLenum face, GLenum pname, const GLfloat param) {
    if(face == GL_BACK || pname != GL_SHININESS) {
        _glKosThrowError(GL_INVALID_ENUM, __func__);
        _glKosPrintError();
        return;
    }

    MATERIAL.exponent = param;
}

void APIENTRY glMateriali(GLenum face, GLenum pname, const GLint param) {
    glMaterialf(face, pname, param);
}

void APIENTRY glMaterialfv(GLenum face, GLenum pname, const GLfloat *params) {
    if(pname == GL_SHININESS) {
        glMaterialf(face, pname, *params);
        return;
    }

    if(face == GL_BACK) {
        _glKosThrowError(GL_INVALID_ENUM, __func__);
        _glKosPrintError();
        return;
    }

    switch(pname) {
        case GL_AMBIENT:
            memcpy(MATERIAL.ambient, params, sizeof(GLfloat) * 4);
        break;
        case GL_DIFFUSE:
            memcpy(MATERIAL.diffuse, params, sizeof(GLfloat) * 4);
        break;
        case GL_SPECULAR:
            memcpy(MATERIAL.specular, params, sizeof(GLfloat) * 4);
        break;
        case GL_EMISSION:
            memcpy(MATERIAL.specular, params, sizeof(GLfloat) * 4);
        break;
        case GL_AMBIENT_AND_DIFFUSE: {
            glMaterialfv(face, GL_AMBIENT, params);
            glMaterialfv(face, GL_DIFFUSE, params);
        } break;
        case GL_COLOR_INDEXES:
        default: {
            _glKosThrowError(GL_INVALID_ENUM, __func__);
            _glKosPrintError();
        }
    }
}

inline void initVec3(struct vec3f* v, const GLfloat* src) {
    memcpy(v, src, sizeof(GLfloat) * 3);
}

/* Fast POW Implementation - Less accurate, but much faster than math.h */
#define EXP_A 184
#define EXP_C 16249

static float FEXP(float y) {
    union {
        float d;
        struct {
            short j, i;
        } n;
    } eco;
    eco.n.i = EXP_A * (y) + (EXP_C);
    eco.n.j = 0;
    return eco.d;
}

static float FLOG(float y) {
    int *nTemp = (int *)&y;
    y = (*nTemp) >> 16;
    return (y - EXP_C) / EXP_A;
}

static float FPOW(float b, float p) {
    return FEXP(FLOG(b) * p);
}

void calculateLightingContribution(const GLint light, const GLfloat* pos, const GLfloat* normal, GLfloat* colour) __attribute__((optimize("fast-math")));
void calculateLightingContribution(const GLint light, const GLfloat* pos, const GLfloat* normal, GLfloat* colour) {
    LightSource* l = &LIGHTS[light];

    struct vec3f L = {
        l->position[0] - pos[0],
        l->position[1] - pos[1],
        l->position[2] - pos[2]
    };

    struct vec3f N = {
        normal[0],
        normal[1],
        normal[2]
    };

    struct vec3f V = {
        pos[0],
        pos[1],
        pos[2]
    };

    GLfloat d;
    vec3f_length(V.x, V.y, V.z, d);

    vec3f_normalize(L.x, L.y, L.z);
    vec3f_normalize(V.x, V.y, V.z);

    GLfloat NdotL;
    vec3f_dot(N.x, N.y, N.z, L.x, L.y, L.z, NdotL);

    GLfloat f = (NdotL < 0) ? 0 : 1;

    GLfloat VdotN;
    vec3f_dot(V.x, V.y, V.z, N.x, N.y, N.z, VdotN);

    GLfloat VdotR = VdotN - NdotL;
    GLfloat specularPower = FPOW(VdotR > 0 ? VdotR : 0, MATERIAL.exponent);

    GLfloat att = (l->position[3] == 0) ? 1.0f : (
        l->constant_attenuation / (1.0f + l->linear_attenuation * d) * (1.0f + l->quadratic_attenuation * d * d)
    );

    colour[0] = att * l->ambient[0] * MATERIAL.ambient[0] + f * (l->diffuse[0] * MATERIAL.diffuse[0] * NdotL + l->specular[0] * MATERIAL.specular[0] * specularPower);
    colour[1] = att * l->ambient[1] * MATERIAL.ambient[1] + f * (l->diffuse[1] * MATERIAL.diffuse[1] * NdotL + l->specular[1] * MATERIAL.specular[1] * specularPower);
    colour[2] = att * l->ambient[2] * MATERIAL.ambient[2] + f * (l->diffuse[2] * MATERIAL.diffuse[2] * NdotL + l->specular[2] * MATERIAL.specular[2] * specularPower);
    colour[3] = MATERIAL.diffuse[3];

    if(colour[0] > 1.0f) colour[0] = 1.0f;
    if(colour[1] > 1.0f) colour[1] = 1.0f;
    if(colour[2] > 1.0f) colour[2] = 1.0f;
    if(colour[3] > 1.0f) colour[3] = 1.0f;
}