/*
* Copyright (C) 2023 Christopher J. Howard
*
* This file is part of Antkeeper source code.
*
* Antkeeper source code is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Antkeeper source code is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Antkeeper source code. If not, see .
*/
#include
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namespace render {
static bool operation_compare(const render::operation* a, const render::operation* b);
shadow_map_pass::shadow_map_pass(gl::rasterizer* rasterizer, resource_manager* resource_manager):
pass(rasterizer, nullptr)
{
// Load unskinned shader template
auto unskinned_shader_template = resource_manager->load("depth-unskinned.glsl");
// Build unskinned shader program
unskinned_shader_program = unskinned_shader_template->build({});
unskinned_model_view_projection_var = unskinned_shader_program->variable("model_view_projection");
// Load skinned shader template
auto skinned_shader_template = resource_manager->load("depth-skinned.glsl");
// Build skinned shader program
skinned_shader_program = skinned_shader_template->build({});
skinned_model_view_projection_var = skinned_shader_program->variable("model_view_projection");
// Calculate bias-tile matrices
float4x4 bias_matrix = math::translate(math::matrix4::identity(), float3{0.5f, 0.5f, 0.5f}) * math::scale(math::matrix4::identity(), float3{0.5f, 0.5f, 0.5f});
float4x4 tile_scale = math::scale(math::matrix4::identity(), float3{0.5f, 0.5f, 1.0f});
for (int i = 0; i < 4; ++i)
{
float x = static_cast(i % 2) * 0.5f;
float y = static_cast(i / 2) * 0.5f;
float4x4 tile_matrix = math::translate(math::matrix4::identity(), float3{x, y, 0.0f}) * tile_scale;
bias_tile_matrices[i] = tile_matrix * bias_matrix;
}
}
void shadow_map_pass::render(render::context& ctx)
{
// For each light
const auto& lights = ctx.collection->get_objects(scene::light::object_type_id);
for (const scene::object_base* object: lights)
{
// Ignore inactive lights
if (!object->is_active())
{
continue;
}
// Ignore non-directional lights
const scene::light& light = static_cast(*object);
if (light.get_light_type() != scene::light_type::directional)
{
continue;
}
// Ignore non-shadow casters
const scene::directional_light& directional_light = static_cast(light);
if (!directional_light.is_shadow_caster())
{
continue;
}
// Ignore improperly-configured lights
if (!directional_light.get_shadow_cascade_count() || !directional_light.get_shadow_framebuffer())
{
continue;
}
// Render cascaded shadow maps
render_csm(directional_light, ctx);
}
}
void shadow_map_pass::render_csm(const scene::directional_light& light, render::context& ctx)
{
rasterizer->use_framebuffer(*light.get_shadow_framebuffer());
// Disable blending
glDisable(GL_BLEND);
// Enable depth testing
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glDepthMask(GL_TRUE);
// Enable back-face culling
glEnable(GL_CULL_FACE);
glCullFace(GL_BACK);
bool two_sided = false;
// For half-z buffer
glDepthRange(-1.0f, 1.0f);
// Get camera
const scene::camera& camera = *ctx.camera;
// Calculate distance to shadow cascade depth clipping planes
const float shadow_clip_far = math::lerp(camera.get_clip_near(), camera.get_clip_far(), light.get_shadow_cascade_coverage());
const unsigned int cascade_count = light.get_shadow_cascade_count();
/// @TODO: don't const_cast
auto& cascade_distances = const_cast&>(light.get_shadow_cascade_distances());
auto& cascade_matrices = const_cast&>(light.get_shadow_cascade_matrices());
// Calculate cascade far clipping plane distances
cascade_distances[cascade_count - 1] = shadow_clip_far;
for (unsigned int i = 0; i < cascade_count - 1; ++i)
{
const float weight = static_cast(i + 1) / static_cast(cascade_count);
// Calculate linear and logarithmic distribution distances
const float linear_distance = math::lerp(camera.get_clip_near(), shadow_clip_far, weight);
const float log_distance = math::log_lerp(camera.get_clip_near(), shadow_clip_far, weight);
// Interpolate between linear and logarithmic distribution distances
cascade_distances[i] = math::lerp(linear_distance, log_distance, light.get_shadow_cascade_distribution());
}
// Calculate viewports for each shadow map
const int shadow_map_resolution = static_cast(light.get_shadow_framebuffer()->get_depth_attachment()->get_width());
const int cascade_resolution = shadow_map_resolution >> 1;
int4 shadow_map_viewports[4];
for (int i = 0; i < 4; ++i)
{
int x = i % 2;
int y = i / 2;
int4& viewport = shadow_map_viewports[i];
viewport[0] = x * cascade_resolution;
viewport[1] = y * cascade_resolution;
viewport[2] = cascade_resolution;
viewport[3] = cascade_resolution;
}
// Reverse half z clip-space coordinates of a cube
constexpr math::vector clip_space_cube[8] =
{
{-1, -1, 1, 1}, // NBL
{ 1, -1, 1, 1}, // NBR
{-1, 1, 1, 1}, // NTL
{ 1, 1, 1, 1}, // NTR
{-1, -1, 0, 1}, // FBL
{ 1, -1, 0, 1}, // FBR
{-1, 1, 0, 1}, // FTL
{ 1, 1, 0, 1} // FTR
};
// Calculate world-space corners of camera view frustum
math::vector view_frustum_corners[8];
for (std::size_t i = 0; i < 8; ++i)
{
math::vector corner = camera.get_inverse_view_projection() * clip_space_cube[i];
view_frustum_corners[i] = math::vector(corner) / corner[3];
}
// Sort render operations
std::sort(std::execution::par_unseq, ctx.operations.begin(), ctx.operations.end(), operation_compare);
gl::shader_program* active_shader_program = nullptr;
for (unsigned int i = 0; i < cascade_count; ++i)
{
// Set viewport for this shadow map
const int4& viewport = shadow_map_viewports[i];
rasterizer->set_viewport(viewport[0], viewport[1], viewport[2], viewport[3]);
// Calculate world-space corners and center of camera subfrustum
const float t_near = (i) ? cascade_distances[i - 1] / camera.get_clip_far() : 0.0f;
const float t_far = cascade_distances[i] / camera.get_clip_far();
math::vector subfrustum_center{0, 0, 0};
math::vector subfrustum_corners[8];
for (std::size_t i = 0; i < 4; ++i)
{
subfrustum_corners[i] = math::lerp(view_frustum_corners[i], view_frustum_corners[i + 4], t_near);
subfrustum_corners[i + 4] = math::lerp(view_frustum_corners[i], view_frustum_corners[i + 4], t_far);
subfrustum_center += subfrustum_corners[i];
subfrustum_center += subfrustum_corners[i + 4];
}
subfrustum_center *= (1.0f / 8.0f);
// Calculate a view-projection matrix from the light's point-of-view
const float3 light_up = light.get_rotation() * config::global_up;
float4x4 light_view = math::look_at(subfrustum_center, subfrustum_center + light.get_direction(), light_up);
float4x4 light_projection = math::ortho(-1.0f, 1.0f, -1.0f, 1.0f, -1.0f, 1.0f);
float4x4 light_view_projection = light_projection * light_view;
// Calculate AABB of the subfrustum corners in light clip-space
geom::box cropping_bounds;
cropping_bounds.min = {std::numeric_limits::infinity(), std::numeric_limits::infinity(), std::numeric_limits::infinity()};
cropping_bounds.max = {-std::numeric_limits::infinity(), -std::numeric_limits::infinity(), -std::numeric_limits::infinity()};
for (std::size_t i = 0; i < 8; ++i)
{
math::vector corner4 = math::vector(subfrustum_corners[i]);
corner4[3] = 1.0f;
corner4 = light_view_projection * corner4;
const math::vector corner3 = math::vector(corner4) / corner4[3];
cropping_bounds.min = math::min(cropping_bounds.min, corner3);
cropping_bounds.max = math::max(cropping_bounds.max, corner3);
}
// Quantize clip-space coordinates
const float texel_scale_x = (cropping_bounds.max.x() - cropping_bounds.min.x()) / static_cast(cascade_resolution);
const float texel_scale_y = (cropping_bounds.max.y() - cropping_bounds.min.y()) / static_cast(cascade_resolution);
cropping_bounds.min.x() = std::floor(cropping_bounds.min.x() / texel_scale_x) * texel_scale_x;
cropping_bounds.max.x() = std::floor(cropping_bounds.max.x() / texel_scale_x) * texel_scale_x;
cropping_bounds.min.y() = std::floor(cropping_bounds.min.y() / texel_scale_y) * texel_scale_y;
cropping_bounds.max.y() = std::floor(cropping_bounds.max.y() / texel_scale_y) * texel_scale_y;
/// @NOTE: light z should be modified here to included shadow casters outside the view frustum
// cropping_bounds.min.z() -= 10.0f;
// cropping_bounds.max.z() += 10.0f;
// Crop light projection matrix
light_projection = math::ortho_half_z
(
cropping_bounds.min.x(), cropping_bounds.max.x(),
cropping_bounds.min.y(), cropping_bounds.max.y(),
cropping_bounds.min.z(), cropping_bounds.max.z()
);
// Recalculate light view projection matrix
light_view_projection = light_projection * light_view;
// Calculate world-space to cascade texture-space transformation matrix
cascade_matrices[i] = bias_tile_matrices[i] * light_view_projection;
for (const render::operation* operation: ctx.operations)
{
const render::material* material = operation->material.get();
if (material)
{
// Skip materials which don't cast shadows
if (material->get_shadow_mode() == material_shadow_mode::none)
{
continue;
}
if (material->is_two_sided() != two_sided)
{
if (material->is_two_sided())
{
glDisable(GL_CULL_FACE);
}
else
{
glEnable(GL_CULL_FACE);
}
two_sided = material->is_two_sided();
}
}
// Switch shader programs if necessary
gl::shader_program* shader_program = (operation->skinning_palette.empty()) ? unskinned_shader_program.get() : skinned_shader_program.get();
if (active_shader_program != shader_program)
{
active_shader_program = shader_program;
rasterizer->use_program(*active_shader_program);
}
// Calculate model-view-projection matrix
float4x4 model_view_projection = light_view_projection * operation->transform;
// Upload operation-dependent parameters to shader program
if (active_shader_program == unskinned_shader_program.get())
{
unskinned_model_view_projection_var->update(model_view_projection);
}
else if (active_shader_program == skinned_shader_program.get())
{
skinned_model_view_projection_var->update(model_view_projection);
}
// Draw geometry
rasterizer->draw_arrays(*operation->vertex_array, operation->drawing_mode, operation->start_index, operation->index_count);
}
}
}
bool operation_compare(const render::operation* a, const render::operation* b)
{
const bool skinned_a = !a->skinning_palette.empty();
const bool skinned_b = !b->skinning_palette.empty();
const bool two_sided_a = (a->material) ? a->material->is_two_sided() : false;
const bool two_sided_b = (b->material) ? b->material->is_two_sided() : false;
if (skinned_a)
{
if (skinned_b)
{
// A and B are both skinned, sort by two-sided
if (two_sided_a)
{
if (two_sided_b)
{
// A and B are both two-sided, sort by VAO
return (a->vertex_array < b->vertex_array);
}
else
{
// A is two-sided, B is one-sided. Render B first
return false;
}
}
else
{
if (two_sided_b)
{
// A is one-sided, B is two-sided. Render A first
return true;
}
else
{
// A and B are both one-sided, sort by VAO
return (a->vertex_array < b->vertex_array);
}
}
}
else
{
// A is skinned, B is unskinned. Render B first
return false;
}
}
else
{
if (skinned_b)
{
// A is unskinned, B is skinned. Render A first
return true;
}
else
{
// A and B are both unskinned, sort by two-sided
if (two_sided_a)
{
if (two_sided_b)
{
// A and B are both two-sided, sort by VAO
return (a->vertex_array < b->vertex_array);
}
else
{
// A is two-sided, B is one-sided. Render B first
return false;
}
}
else
{
if (two_sided_b)
{
// A is one-sided, B is two-sided. Render A first
return true;
}
else
{
// A and B are both one-sided, sort by VAO
return (a->vertex_array < b->vertex_array);
}
}
}
}
}
} // namespace render