suicmez/game/inc/suic_lighting.c

#include "suic_lighting.h"
#include "suic_terrain.h"
#include <math.h>

SuicDirectionalLight suic_light_create(float dir_x, float dir_y, float dir_z,
                                       float intensity, float ambient) {
  SuicDirectionalLight light = {0};
  light.direction = suic_v3_norm(suic_v3(dir_x, dir_y, dir_z));
  light.color = suic_v3(1.0f, 1.0f, 1.0f);
  light.intensity = intensity;
  light.ambientIntensity = ambient;
  light.shadowBias = 0.005f;
  light.shadowIntensity = 0.4f;
  return light;
}

SuicDirectionalLight suic_light_create_default(void) {
  return suic_light_create(-0.8f, -1.0f, -0.6f, 1.2f, 0.3f);
}

SuicColor suic_light_apply(SuicColor base, SuicVec3 normal,
                           SuicDirectionalLight *light) {
  SuicVec3 lightDir = light->direction;

  /* Diffuse: Lambertian */
  float diff = fmaxf(0.0f, -(lightDir.x * normal.x + lightDir.y * normal.y +
                             lightDir.z * normal.z));

  float brightness =
      light->ambientIntensity +
      (diff * light->intensity * (1.0f - light->ambientIntensity));

  int r = (int)(base.r * brightness);
  int g = (int)(base.g * brightness);
  int b = (int)(base.b * brightness);

  if (r > 255)
    r = 255;
  if (g > 255)
    g = 255;
  if (b > 255)
    b = 255;

  return (SuicColor){r, g, b, base.a};
}

float suic_shadow_factor(SuicVec3 worldPos, SuicVec3 lightDir, float maxDist) {
  float distFromLight = fmaxf(0.0f, worldPos.y - 2.0f);
  float shadowIntensity = fmaxf(0.0f, 1.0f - (distFromLight / maxDist));
  return 1.0f - (shadowIntensity * 0.15f);
}

float suic_shadow_temporal(SuicVec3 worldPos, float timePhase) {
  float noiseVal =
      sinf(worldPos.x * 0.5f + timePhase) * cosf(worldPos.z * 0.5f + timePhase);
  return 1.0f + (noiseVal * 0.02f);
}

SuicColor suic_light_apply_shadows(SuicColor base, SuicVec3 normal,
                                   SuicVec3 worldPos,
                                   SuicDirectionalLight *light) {
  float shadowFactor = suic_shadow_factor(worldPos, light->direction, 10.0f);
  float adjustedIntensity = light->intensity * shadowFactor;

  SuicVec3 lightDir = light->direction;
  float diff = fmaxf(0.0f, -(lightDir.x * normal.x + lightDir.y * normal.y +
                             lightDir.z * normal.z));

  float brightness =
      light->ambientIntensity +
      (diff * adjustedIntensity * (1.0f - light->ambientIntensity));

  int r = (int)(base.r * brightness);
  int g = (int)(base.g * brightness);
  int b = (int)(base.b * brightness);

  if (r > 255)
    r = 255;
  if (g > 255)
    g = 255;
  if (b > 255)
    b = 255;

  return (SuicColor){r, g, b, base.a};
}

float suic_ao_calculate(SuicVec3 worldPos, SuicVec3 normal) {
  float sampleRadius = 3.0f;
  float aoAccum = 0.0f;
  int numSamples = 8;
  float centerHeight = worldPos.y;
  float pi = 3.14159265f;

  for (int i = 0; i < numSamples; i++) {
    float angle = (2.0f * pi * (float)i) / (float)numSamples;
    float sx = worldPos.x + cosf(angle) * sampleRadius;
    float sz = worldPos.z + sinf(angle) * sampleRadius;
    float sh = suic_terrain_height(sx, sz);

    float heightDiff = sh - centerHeight;
    if (heightDiff > 0.1f) {
      float aoAmount = fminf(1.0f, heightDiff / 2.0f);
      aoAccum += aoAmount;
    }
  }

  float aoFactor = 1.0f - (aoAccum / (float)numSamples) * 0.6f;
  return fmaxf(0.2f, aoFactor);
}

SuicColor suic_light_apply_phong(SuicColor base, SuicVec3 normal,
                                 SuicVec3 worldPos, SuicVec3 camPos,
                                 SuicDirectionalLight *light) {
  SuicVec3 lightDir = suic_v3_norm(light->direction);
  SuicVec3 normal_n = suic_v3_norm(normal);
  SuicVec3 viewDir = suic_v3_norm(suic_v3_sub(camPos, worldPos));

  /* Diffuse */
  float diffuse = fmaxf(0.0f, -suic_v3_dot(lightDir, normal_n));

  /* Specular: Blinn-Phong */
  SuicVec3 negLight = suic_v3(-lightDir.x, -lightDir.y, -lightDir.z);
  SuicVec3 halfVec = suic_v3_norm(suic_v3_add(suic_v3_norm(negLight), viewDir));
  float specular =
      powf(fmaxf(0.0f, suic_v3_dot(halfVec, normal_n)), 32.0f) * 0.5f;

  /* Ambient occlusion */
  float ao = suic_ao_calculate(worldPos, normal_n);

  /* Shadow */
  float shadowFactor = suic_shadow_factor(worldPos, light->direction, 10.0f);

  /* Combine */
  float brightness = light->ambientIntensity * ao;
  brightness += diffuse * light->intensity * shadowFactor *
                (1.0f - light->ambientIntensity) * ao;
  brightness += specular * light->intensity * shadowFactor * 0.6f;

  brightness = fminf(1.0f, brightness);

  int r = (int)(base.r * brightness);
  int g = (int)(base.g * brightness);
  int b = (int)(base.b * brightness);

  if (r > 255)
    r = 255;
  if (g > 255)
    g = 255;
  if (b > 255)
    b = 255;

  return (SuicColor){r, g, b, base.a};
}