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192 | -- SPDX-License-Identifier: Apache-2.0
--
-- Copyright (c) 2020 onox <denkpadje@gmail.com>
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
-- http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.
with Ada.Characters.Latin_1;
with Ada.Numerics.Generic_Elementary_Functions;
with GL.Buffers;
with GL.Types;
with Orka.Rendering.Drawing;
with Orka.Transforms.Doubles.Matrices;
with Orka.Transforms.Doubles.Vectors;
with Orka.Transforms.Doubles.Vector_Conversions;
with Orka.Transforms.Singles.Vectors;
package body Orka.Features.Atmosphere.Rendering is
package L1 renames Ada.Characters.Latin_1;
package EF is new Ada.Numerics.Generic_Elementary_Functions (Float_64);
Altitude_Hack_Threshold : constant := 8000.0;
function Create_Atmosphere
(Data : aliased Model_Data;
Location : Resources.Locations.Location_Ptr;
Parameters : Model_Parameters := (others => <>)) return Atmosphere
is
Atmosphere_Model : constant Model := Create_Model (Data, Location);
Sky_GLSL : constant String := Resources.Convert
(Orka.Resources.Byte_Array'(Location.Read_Data ("atmosphere/sky.frag").Get));
use Rendering.Programs;
use Rendering.Programs.Modules;
Sky_Shader : constant String :=
"#version 420 core" & L1.LF &
(if Data.Luminance /= None then "#define USE_LUMINANCE" & L1.LF else "") &
"const float kLengthUnitInMeters = " & Data.Length_Unit_In_Meters'Image & ";" & L1.LF &
Sky_GLSL & L1.LF;
Shader_Module : constant Rendering.Programs.Modules.Module := Atmosphere_Model.Get_Shader;
begin
return Result : Atmosphere :=
(Program => Create_Program (Modules.Module_Array'
(Modules.Create_Module (Location, VS => "atmosphere/sky.vert"),
Modules.Create_Module_From_Sources (FS => Sky_Shader),
Shader_Module)),
Module => Shader_Module,
Parameters => Parameters,
Bottom_Radius => Data.Bottom_Radius,
Distance_Scale => 1.0 / Data.Length_Unit_In_Meters,
others => <>)
do
Result.Uniform_Ground_Hack := Result.Program.Uniform ("ground_hack");
Result.Uniform_Camera_Offset := Result.Program.Uniform ("camera_offset");
Result.Uniform_Camera_Pos := Result.Program.Uniform ("camera_pos");
Result.Uniform_Planet_Pos := Result.Program.Uniform ("planet_pos");
Result.Uniform_View := Result.Program.Uniform ("view");
Result.Uniform_Proj := Result.Program.Uniform ("proj");
Result.Uniform_Sun_Dir := Result.Program.Uniform ("sun_direction");
Result.Uniform_Star_Dir := Result.Program.Uniform ("star_direction");
Result.Uniform_Star_Size := Result.Program.Uniform ("star_size");
end return;
end Create_Atmosphere;
function Shader_Module (Object : Atmosphere) return Orka.Rendering.Programs.Modules.Module is
(Object.Module);
function Flattened_Vector
(Parameters : Model_Parameters;
Direction : Orka.Transforms.Doubles.Vectors.Vector4)
return Orka.Transforms.Doubles.Vectors.Vector4 is
Altitude : constant := 0.0;
Flattening : Float_64 renames Parameters.Flattening;
E2 : constant Float_64 := 2.0 * Flattening - Flattening**2;
N : constant Float_64 := Parameters.Semi_Major_Axis /
EF.Sqrt (1.0 - E2 * Direction (Orka.Z)**2);
begin
return
(Direction (Orka.X) * (N + Altitude),
Direction (Orka.Y) * (N + Altitude),
Direction (Orka.Z) * (N * (1.0 - E2) + Altitude),
1.0);
end Flattened_Vector;
package Matrices renames Orka.Transforms.Doubles.Matrices;
procedure Render
(Object : in out Atmosphere;
Camera : Cameras.Camera_Ptr;
Planet : Behaviors.Behavior_Ptr;
Star : Behaviors.Behavior_Ptr)
is
use all type GL.Types.Compare_Function;
function "*" (Left : Matrices.Matrix4; Right : Matrices.Vector4) return Matrices.Vector4
renames Matrices."*";
function "*" (Left, Right : Matrices.Matrix4) return Matrices.Matrix4 renames Matrices."*";
function Far_Plane (Value : GL.Types.Compare_Function) return GL.Types.Compare_Function is
(case Value is
when Less | LEqual => LEqual,
when Greater | GEqual => GEqual,
when others => raise Constraint_Error);
Original_Function : constant GL.Types.Compare_Function := GL.Buffers.Depth_Function;
use Orka.Transforms.Doubles.Vectors;
use Orka.Transforms.Doubles.Vector_Conversions;
use all type Orka.Transforms.Doubles.Vectors.Vector4;
Planet_To_Camera : constant Vector4 := Camera.View_Position - Planet.Position;
Planet_To_Star : constant Vector4 := Star.Position - Planet.Position;
Camera_To_Star : constant Vector4 := Star.Position - Camera.View_Position;
procedure Apply_Hacks is
GL_To_Geo : constant Matrices.Matrix4 := Matrices.R
(Matrices.Vectors.Normalize ((1.0, 1.0, 1.0, 0.0)),
(2.0 / 3.0) * Ada.Numerics.Pi);
Earth_Tilt : constant Matrices.Matrix4 := Matrices.R
(Matrices.Vectors.Normalize ((1.0, 0.0, 0.0, 0.0)),
Object.Parameters.Axial_Tilt);
Inverse_Inertial : constant Matrices.Matrix4 := Earth_Tilt * GL_To_Geo;
Camera_Normal_Inert : constant Vector4 := Normalize (Inverse_Inertial * Planet_To_Camera);
Actual_Surface : constant Vector4 := Flattened_Vector
(Object.Parameters, Camera_Normal_Inert);
Expected_Surface : constant Vector4 := Camera_Normal_Inert * Object.Bottom_Radius;
Offset : constant Vector4 := Expected_Surface - Actual_Surface;
Altitude : constant Float_64 := Norm (Planet_To_Camera) - Norm (Actual_Surface);
begin
Object.Uniform_Ground_Hack.Set_Boolean (Altitude < Altitude_Hack_Threshold);
Object.Uniform_Camera_Offset.Set_Vector (Convert (Offset * Object.Distance_Scale));
end Apply_Hacks;
begin
if Object.Parameters.Flattening > 0.0 then
Apply_Hacks;
else
Object.Uniform_Ground_Hack.Set_Boolean (False);
Object.Uniform_Camera_Offset.Set_Vector (Orka.Transforms.Singles.Vectors.Zero_Vector);
end if;
Object.Uniform_Camera_Pos.Set_Vector (Orka.Transforms.Singles.Vectors.Zero_Vector);
Object.Uniform_Planet_Pos.Set_Vector (Convert (-Planet_To_Camera * Object.Distance_Scale));
Object.Uniform_Sun_Dir.Set_Vector (Convert (Normalize (Planet_To_Star)));
Object.Uniform_Star_Dir.Set_Vector (Convert (Normalize (Camera_To_Star)));
-- Use distance to star and its radius instead of the
-- Sun_Angular_Radius of Model_Data
declare
Angular_Radius : constant Float_64 :=
EF.Arctan (Object.Parameters.Star_Radius, Norm (Camera_To_Star));
begin
Object.Uniform_Star_Size.Set_Single (Float_32 (EF.Cos (Angular_Radius)));
end;
Object.Uniform_View.Set_Matrix (Camera.View_Matrix);
Object.Uniform_Proj.Set_Matrix (Camera.Projection_Matrix);
Object.Program.Use_Program;
GL.Buffers.Set_Depth_Function (Far_Plane (Original_Function));
Orka.Rendering.Drawing.Draw (GL.Types.Triangles, 0, 3);
GL.Buffers.Set_Depth_Function (Original_Function);
end Render;
end Orka.Features.Atmosphere.Rendering;
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