RustPhysicsMQ/src/shaders/shader.frag

#version 330 core

in vec4 v_normal;
in vec4 color;
in vec3 light_direction;
in vec4 v_light_space_position; // New: Position transformed by LightSpaceMatrix

uniform int render_normals_bool;
uniform int render_shadows_bool;
uniform sampler2D shadow_map; // New: Depth map texture

out vec4 FragColor;

const float ambient_strenght = 0.3;
const float diffuse_strenght = 0.7;

/**
 * Calculates the shadow factor (0.0 for shadow, 1.0 for lit).
 */
float calculate_shadow() {
        float min_bias = 0.003;
        float max_bias = 0.01;
        float dot_product = dot(normalize(v_normal.xyz), normalize(light_direction));
        float bias = max(max_bias * (1.0 - dot_product), min_bias);

        // float bias = 0;

        // 1. Perspective divide to get Normalized Device Coordinates (NDC)
        vec3 proj_coords = v_light_space_position.xyz / v_light_space_position.w;

        // 2. Transform to texture coordinates (0 to 1 range)
        vec2 tex_coords = proj_coords.xy * 0.5 + 0.5;

        // 3. Get the closest depth from the light's perspective (shadow map)
        // We sample the red channel since Macroquad's depth texture stores depth data there.
        float closest_depth = texture(shadow_map, tex_coords).r;

        // 4. Get the current fragment's depth from the light's perspective
        // float current_depth = proj_coords.z;
        float current_depth = proj_coords.z * 0.5 + 0.5;
        // float current_depth = v_light_space_position.z;
        // 5. Check if the fragment is outside the light frustum
        if (tex_coords.x > 1.0 || tex_coords.x < 0.0 || tex_coords.y > 1.0 || tex_coords.y < 0.0 || current_depth > 1.0) {
                return 1.0;
        }

        // float shadow = 0.0;
        // vec2 texelSize = 1.0 / textureSize(shadow_map, 0);
        // int x_ran = 1;
        // for (int x = -x_ran; x <= x_ran; x++)
        // {
        //         for (int y = -x_ran; y <= x_ran; y++)
        //         {
        //                 float pcfDepth = texture(shadow_map, tex_coords + vec2(x, y) * texelSize).x;
        //                 shadow += current_depth - bias > pcfDepth ? 0.0 : 1.0;
        //         }
        // }
        // shadow = current_depth - bias > closest_depth ? 0.0 : 1.0;

        // shadow /= ((2 * x_ran) + 1) * ((2 * x_ran) + 1);

        // 6. Compare depths with a bias: if current depth > closest depth, we are in shadow (0.0)
        float shadow = current_depth - bias > closest_depth ? 0.0 : 1.0;

        return min(max(shadow, 0), 1);
}

void main() {
        float diff = max(dot(normalize(vec3(v_normal.x, v_normal.y, v_normal.z)), normalize(light_direction)), 0) * diffuse_strenght;

        if (render_normals_bool == 1) {
                FragColor = vec4(v_normal);
                return;
        }
        if (render_shadows_bool == 1) {
                float lighting = ambient_strenght + diff;
                FragColor = normalize(v_normal) * lighting;
                return;
        }

        float shadow_factor = calculate_shadow();

        float lighting = ambient_strenght + diff * shadow_factor;

        FragColor = normalize(abs(v_normal)) * lighting;
}