Animated the thrust flame

data/shaders/opengl/thruster.frag

@@ -0,0 +1,27 @@
+// Copyright © 2008-2025 Pioneer Developers. See AUTHORS.txt for details
+// Licensed under the terms of the GPL v3. See licenses/GPL-3.txt
+
+#include "attributes.glsl"
+#include "lib.glsl"
+
+uniform sampler2D texture0; //diffuse
+
+in vec2 texCoord0;
+in vec4 flame_color;
+in float ramp;
+
+out vec4 frag_color;
+
+void main(void)
+{
+	vec4 color = texture(texture0, texCoord0);
+	vec3 old_color = color.rgb;
+	color *= flame_color;
+	// generate a light blue flickering glow around the flame
+	float ramp2 = ramp * ramp;
+	color.g += ramp2 * ramp2 * old_color.g;
+	color.r += ramp2 * ramp * old_color.r;
+	color.b += ramp2 * old_color.b;
+
+	frag_color = color;
+}

data/shaders/opengl/thruster.shaderdef

@@ -0,0 +1,12 @@
+## Copyright © 2008-2025 Pioneer Developers. See AUTHORS.txt for details
+## Licensed under the terms of the GPL v3. See licenses/GPL-3.txt
+
+# Basic shader for drawing unlit, possibly textured models that are animated
+
+Shader thruster
+
+Texture sampler2D texture0 name=diffuse
+Buffer DrawData binding=1
+
+Vertex "thruster.vert"
+Fragment "thruster.frag"

data/shaders/opengl/thruster.vert

@@ -0,0 +1,46 @@
+// Copyright © 2008-2025 Pioneer Developers. See AUTHORS.txt for details
+// Licensed under the terms of the GPL v3. See licenses/GPL-3.txt
+
+// #extension GL_ARB_gpu_shader5 : enable
+
+#include "attributes.glsl"
+#include "lib.glsl"
+
+out vec2 texCoord0;
+out vec4 flame_color;
+out float ramp;
+
+float map_percentage( float val, float base_percent)
+{
+   return base_percent + val * (1.0 - base_percent);
+}
+
+void main(void)
+{
+	// emission.r is the thruster power setting
+	float thruster_power = material.emission.r;
+	// emission.a is the random flicker value
+	float random = material.emission.a;
+
+	// power setting effects the brightness and opacity of the flame
+	float brightness = map_percentage(thruster_power, 0.25);
+	// flicker should only change the brightness a small amount each frame
+	float flicker = map_percentage(random, 0.95);
+
+	flame_color = material.diffuse * flicker * brightness;
+	// a very light blue flickering glow around flame
+	flame_color.rg *= vec2(flicker);
+
+	// the power setting also controls the length of the flame
+	// flame length can range from 50% to 100%
+	float flame_length = map_percentage(thruster_power, 0.5);
+	// modulate the flame shape using flicker
+	// flame_length only effects the z axis which is the thrust direction
+	vec4 scale = vec4(flicker, flicker, flicker * flame_length, 1.0);
+
+	gl_Position = uViewProjectionMatrix * (a_vertex * scale);
+
+	texCoord0 = a_uv0.xy;
+	// set the blend ramp
+	ramp = a_uv0.y * 0.5;
+}

src/Intro.cpp

@@ -160,5 +160,8 @@ void Intro::Draw(float deltaTime)
 		matrix4x4f::Translation(0, 0, m_dist) *
 		matrix4x4f::RotateXMatrix(DEG2RAD(-15.0f)) *
 		matrix4x4f::RotateYMatrix(duration);
+
+	// animate thrusters
+	m_model->SetTimeStep(duration);
 	m_model->Render(trans);
 }

src/ShipCockpit.cpp

@@ -195,6 +195,8 @@ void ShipCockpit::Update(const Player *player, float timeStep)
 		vector3f linthrust{ prop->GetLinThrusterState() };
 		vector3f angthrust{ prop->GetAngThrusterState() };
 		GetModel()->SetThrust(linthrust, -angthrust);
+		// animate the thrusters
+		GetModel()->SetTimeStep(timeStep);
 	}
 }
 

src/editor/ModelViewerWidget.cpp

@@ -575,6 +575,7 @@ void ModelViewerWidget::DrawModel(matrix4x4f trans)
 		(m_options.showGeomBBox ? SceneGraph::Model::DEBUG_GEOMBBOX : 0x0) |
 		(m_options.wireframe ? SceneGraph::Model::DEBUG_WIREFRAME : 0x0));
 
+	m_model->SetTimeStep(0.01f);
 	m_model->Render(m_modelViewMat);
 	m_navLights->Render(m_renderer);
 }

src/scenegraph/Model.cpp

@@ -150,6 +150,9 @@ namespace SceneGraph {
 		//Override renderdata if this model is called from ModelNode
 		RenderData params = (rd != 0) ? (*rd) : m_renderData;
 
+		// reset time step for next frame
+		m_renderData.timeStep = 0.f;
+
 		m_renderer->SetTransform(trans);
 
 		//using the entire model bounding radius for all nodes at the moment.
@@ -212,6 +215,9 @@ namespace SceneGraph {
 		//Override renderdata if this model is called from ModelNode
 		RenderData params = (rd != 0) ? (*rd) : m_renderData;
 
+		// reset time step
+		m_renderData.timeStep = 0.f;
+
 		//using the entire model bounding radius for all nodes at the moment.
 		//BR could also be a property of Node.
 		params.boundingRadius = GetDrawClipRadius();
@@ -434,6 +440,11 @@ namespace SceneGraph {
 		m_renderData.angthrust[2] = ang.z;
 	}
 
+	void Model::SetTimeStep(const float timeStep)
+	{
+		m_renderData.timeStep = timeStep;
+	}
+
 	void Model::SetThrusterColor(const vector3f &dir, const Color &color)
 	{
 		assert(m_root != nullptr);

src/scenegraph/Model.h

@@ -172,6 +172,7 @@ namespace SceneGraph {
 		Graphics::Renderer *GetRenderer() const { return m_renderer; }
 
 		//special for ship model use
+		void SetTimeStep(const float timeStep);
 		void SetThrust(const vector3f &linear, const vector3f &angular);
 
 		void SetThrusterColor(const vector3f &dir, const Color &color);

src/scenegraph/Node.h

@@ -48,13 +48,15 @@ namespace SceneGraph {
 		float linthrust[3]; // 1.0 to -1.0
 		float angthrust[3]; // 1.0 to -1.0
 		Color customColor;
+		float timeStep; // used as a heart beat for shaders
 
 		float boundingRadius; //updated by model and passed to submodels
 		unsigned int nodemask;
 
 		RenderData() :
 			linthrust(),
 			angthrust(),
+			timeStep(0.f),
 			boundingRadius(0.f),
 			nodemask(NODE_SOLID) //draw solids
 		{

src/scenegraph/Thruster.cpp

@@ -29,7 +29,8 @@ namespace SceneGraph {
 		linearOnly(_linear),
 		dir(_dir),
 		pos(_pos),
-		currentColor(baseColor)
+		currentColor(baseColor),
+		m_time(0.f)
 	{
 		//set up materials
 		Graphics::MaterialDescriptor desc;
@@ -41,12 +42,12 @@ namespace SceneGraph {
 		rsd.depthWrite = false;
 		rsd.cullMode = Graphics::CULL_NONE;
 
-		m_tMat.Reset(r->CreateMaterial("unlit", desc, rsd));
+		m_tMat.Reset(r->CreateMaterial("thruster", desc, rsd));
 		m_tMat->SetTexture("texture0"_hash,
 			Graphics::TextureBuilder::Billboard(thrusterTextureFilename).GetOrCreateTexture(r, "billboard"));
 		m_tMat->diffuse = baseColor;
 
-		m_glowMat.Reset(r->CreateMaterial("unlit", desc, rsd));
+		m_glowMat.Reset(r->CreateMaterial("thruster", desc, rsd));
 		m_glowMat->SetTexture("texture0"_hash,
 			Graphics::TextureBuilder::Billboard(thrusterGlowTextureFilename).GetOrCreateTexture(r, "billboard"));
 		m_glowMat->diffuse = baseColor;
@@ -59,7 +60,8 @@ namespace SceneGraph {
 		linearOnly(thruster.linearOnly),
 		dir(thruster.dir),
 		pos(thruster.pos),
-		currentColor(thruster.currentColor)
+		currentColor(thruster.currentColor),
+		m_time(thruster.m_time)
 	{
 	}
 
@@ -100,8 +102,24 @@ namespace SceneGraph {
 			}
 		}
 		if (power < 0.001f) return;
-
-		m_tMat->diffuse = m_glowMat->diffuse = currentColor * power;
+
+		// animate the thrust flame using the thruster shader
+		// update animation time on each render
+		// a unique time stamp is needed for each thruster flame to have a unique flicker
+		// use thruster position to make each thruster time different
+		m_time += abs(trans[12] + trans[13] + trans[14]) * rd->timeStep * 1000.0f;
+		// generate a psuedo random flicker
+		// this could be done in the vertex shader but the value only needs to be 
+		// generated once per frame, not for every vertex
+		const float flicker = sin(m_time) * 43758.5453f;
+
+		// pass the power setting and flicker value using the material emissive
+		// emissive.a is the flicker value for the flame
+		m_tMat->emissive.a = m_glowMat->emissive.a = flicker;
+		// emissive.r is the thruster power setting which effects flame length and brightness
+		m_tMat->emissive.r = m_glowMat->emissive.r = 255.0f * power;
+
+		m_tMat->diffuse = m_glowMat->diffuse = currentColor;
 
 		//directional fade
 		vector3f cdir = vector3f(trans * -dir).Normalized();

src/scenegraph/Thruster.h

@@ -44,6 +44,7 @@ namespace SceneGraph {
 		vector3f dir;
 		vector3f pos;
 		Color currentColor;
+		float m_time; // used for animating the thruster
 	};
 
 } // namespace SceneGraph

src/ship/Propulsion.cpp

@@ -241,7 +241,10 @@ void Propulsion::Render(Graphics::Renderer *r, const Camera *camera, const vecto
 	 * thruster and so on)... this code is :-/
 	*/
 	//angthrust negated, for some reason
-	if (m_smodel != nullptr) m_smodel->SetThrust(vector3f(GetLinThrusterState()), -vector3f(GetAngThrusterState()));
+	if (m_smodel != nullptr) {
+		m_smodel->SetThrust(vector3f(GetLinThrusterState()), -vector3f(GetAngThrusterState()));
+		m_smodel->SetTimeStep(Pi::game->GetTimeStep());
+	}
 }
 
 void Propulsion::AIModelCoordsMatchSpeedRelTo(const vector3d &v, const DynamicBody *other)