Add BillboardProgram to SceneShader

The implementation is overly simple/incomplete, I'm not even convince
what is there is right, but it's a decent start.

5 files changed, 77 insertions, 1 deletions

diff --git a/gfx/gl/sceneRenderer.cpp b/gfx/gl/sceneRenderer.cpp
index 463ee8a..e693787 100644
--- a/gfx/gl/sceneRenderer.cpp
+++ b/gfx/gl/sceneRenderer.cpp
@@ -107,6 +107,7 @@ SceneRenderer::render(const SceneProvider & scene) const
 		glEnable(GL_DEPTH_TEST);
 		glClearColor(0, 0, 0, 1);
 		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+		glEnable(GL_PROGRAM_POINT_SIZE);
 		scene.content(shader, camera);
 	}
 
diff --git a/gfx/gl/sceneShader.cpp b/gfx/gl/sceneShader.cpp
index 72cde91..43e54a5 100644
--- a/gfx/gl/sceneShader.cpp
+++ b/gfx/gl/sceneShader.cpp
@@ -1,4 +1,6 @@
 #include "sceneShader.h"
+#include <gfx/gl/shaders/billboard-frag.h>
+#include <gfx/gl/shaders/billboard-vert.h>
 #include <gfx/gl/shaders/dynamicPoint-vert.h>
 #include <gfx/gl/shaders/dynamicPointInst-vert.h>
 #include <gfx/gl/shaders/fixedPoint-vert.h>
@@ -30,7 +32,7 @@ inline void
 SceneShader::allPrograms(auto member, auto &&... ps) const
 {
 	for (const auto & prog : std::initializer_list<const SceneProgram *> {&basic, &basicInst, &water, &landmass,
-				 &absolute, &pointLightInst, &spotLightInst, &networkStraight, &networkCurve}) {
+				 &absolute, &pointLightInst, &spotLightInst, &networkStraight, &networkCurve, &billboard}) {
 		(prog->*member)(std::forward<decltype(ps)>(ps)...);
 	}
 }
@@ -89,6 +91,16 @@ SceneShader::BasicProgram::use(Location const & location) const
 	setModel(location);
 }
 
+SceneShader::BillboardProgram::BillboardProgram() : SceneProgram {billboard_vert, billboard_frag} { }
+
+void
+SceneShader::BillboardProgram::use(RelativeDistance size, RelativePosition3D centre) const
+{
+	Program::use();
+	glUniform(sizeLoc, size);
+	glUniform(centreLoc, centre);
+}
+
 void
 SceneShader::LandmassProgram::use(const glm::vec3 colourBias) const
 {
diff --git a/gfx/gl/sceneShader.h b/gfx/gl/sceneShader.h
index 47d4397..faba4a4 100644
--- a/gfx/gl/sceneShader.h
+++ b/gfx/gl/sceneShader.h
@@ -32,6 +32,17 @@ class SceneShader {
 		RequiredUniformLocation modelPosLoc {*this, "modelPos"};
 	};
 
+	class BillboardProgram : public SceneProgram {
+	public:
+		BillboardProgram();
+
+		void use(RelativeDistance size, RelativePosition3D centre) const;
+
+	private:
+		RequiredUniformLocation sizeLoc {*this, "size"};
+		RequiredUniformLocation centreLoc {*this, "centre"};
+	};
+
 	class AbsolutePosProgram : public SceneProgram {
 	public:
 		using Program::use;
@@ -74,6 +85,7 @@ public:
 	BasicProgram basic;
 	WaterProgram water;
 	AbsolutePosProgram basicInst, absolute, spotLightInst, pointLightInst;
+	BillboardProgram billboard;
 	LandmassProgram landmass;
 	NetworkProgram networkStraight, networkCurve;
 
diff --git a/gfx/gl/shaders/billboard.frag b/gfx/gl/shaders/billboard.frag
new file mode 100644
index 0000000..1e2c4ae
--- /dev/null
+++ b/gfx/gl/shaders/billboard.frag
@@ -0,0 +1,28 @@
+#version 460 core
+
+const float tau = 6.28318531;
+
+layout(binding = 0) uniform sampler2DArray billboardDepth;
+layout(binding = 1) uniform sampler2DArray billboardNormal;
+layout(binding = 2) uniform sampler2DArray billboardAlbedo;
+uniform mat4 viewProjection;
+uniform float size;
+
+include(`materialOut.glsl')
+
+flat in ivec3 ModelPos;
+flat in float Yaw;
+flat in float Depth;
+
+void
+main()
+{
+	int viewAngle = int(round(8 * Yaw / tau)) % 8;
+	vec3 texel = vec3(gl_PointCoord * vec2(-1, 1) + vec2(1, 0), viewAngle);
+	gAlbedoSpec = texture(billboardAlbedo, texel);
+	if (gAlbedoSpec.a < 0.5) {
+		discard;
+	}
+	gPosition = ivec4(ModelPos + vec3(0, 0, size * 2 * (1 - gl_PointCoord.y)), 1);
+	gNormal = texture(billboardNormal, texel) * vec4(-1, -1, 1, 1);
+}
diff --git a/gfx/gl/shaders/billboard.vert b/gfx/gl/shaders/billboard.vert
new file mode 100644
index 0000000..2d73084
--- /dev/null
+++ b/gfx/gl/shaders/billboard.vert
@@ -0,0 +1,23 @@
+#version 460 core
+
+uniform mat4 viewProjection;
+uniform ivec4 viewPort;
+uniform ivec3 viewPoint;
+uniform vec3 centre;
+uniform float size;
+layout(location = 0) in ivec3 modelPos;
+layout(location = 1) in float yaw;
+
+flat out ivec3 ModelPos;
+flat out float Yaw;
+flat out float Depth;
+
+void
+main()
+{
+	ModelPos = modelPos;
+	Yaw = yaw;
+	gl_Position = viewProjection * vec4(modelPos - viewPoint + centre, 1);
+	Depth = gl_Position.w;
+	gl_PointSize = (viewPort.w * size * 2) / gl_Position.w;
+}