class RenderList

A RenderList is a collection of Draw commands that can be submitted to various surfaces. RenderList.Primary is where all normal Draw calls get added to, and this RenderList is renderer to primary display surface.

Manually working with a RenderList can be useful for “baking down matrices” or caching a scene of objects. Or for drawing a separate scene to an offscreen surface, like for thumbnails of Models.

Instance Fields and Properties


int Count	The number of Mesh/Material pairs that have been submitted to the render list so far this frame.
string Id	Gets or sets the unique identifier of this asset resource! This can be helpful for debugging, managing your assets, or finding them later on!
int PrevCount	This is the number of items in the RenderList before it was most recently cleared. If this is a list that is drawn and cleared each frame, you can think of this as “last frame’s count”.

Instance Methods


RenderList	Creates a new empty RenderList.
Add	Add a Mesh/Material to the RenderList. The RenderList will hold a reference to these Assets until the list is cleared.
Clear	Clears out and de-references all Draw items currently in the RenderList.
DrawNow	Draws the RenderList to a rendertarget texture immediately. It does not clear the list.

Static Fields and Properties


RenderList Primary	The default RenderList used by the Renderer for the primary display surface.

Static Methods


Find	Finds the RenderList with the matching id, and returns a reference to it. If no RenderList is found, it returns null.
Pop	This removes the current top of the RenderList stack, making the next list as active
Push	All draw calls that don’t specify a render list will get submitted to the active RenderList at the top of the stack. By default, that’s RenderList.Primary, but you can push your own list onto the stack here to capture draw calls, like those done in the UI.

Examples

Render Icon From a Model

UI with a custom rendererd icon

One place where RenderList excels, is at rendering icons or previews of Models or scenes! This snippet of code will take a Model asset, and render a preview of it into a small Sprite.

static Sprite MakeIcon(Model model, int resolution)
{
	RenderList list   = new RenderList();
	Tex        result = Tex.RenderTarget(resolution, resolution, 8);

	// Calculate a standard size that will fill the icon to the edges,
	// based on the camera parameters we pass to DrawNow.
	float scale = 1/model.Bounds.dimensions.Length;

	list.Add(model, Matrix.TS(-model.Bounds.center*scale, scale), Color.White);

	// OpenGL renders upside-down to rendertargets, so this is a simple fix
	// for our case here, we just flip the camera upside down.
	Vec3 up = Backend.Graphics == BackendGraphics.D3D11
		?  Vec3.Up
		: -Vec3.Up;
	list.DrawNow(result,
		Matrix.LookAt(V.XYZ(0,0,-1), Vec3.Zero, up),
		Matrix.Perspective(45, 1, 0.01f, 10));

	// Clearing isn't _necessary_ here, but DrawNow does not clear the list
	// after drawing! This will free up assets that were referenced in the
	// list without waiting for GC to destroy the RenderList object.
	list.Clear();

	return Sprite.FromTex(result.Copy());
}

From there, it’s pretty easy to load a Model up, and draw it on a button in the UI.

Sprite icon;
public void Initialize()
{
	Model model = Model.FromFile("Watermelon.glb");
	// Model loading is async, so we want to make sure the Model is fully
	// loaded before comitting it to a Sprite!
	Assets.BlockForPriority(int.MaxValue);
	icon = MakeIcon(model, 128);
}

Pose windowPose = new Pose(0,0,-0.5f, Quat.LookDir(0,0,1));
void ShowWindow()
{
	UI.WindowBegin("RenderList Icons", ref windowPose);
	UI.ButtonImg("Icon", icon, UIBtnLayout.CenterNoText, V.XX(UI.LineHeight*2));
	UI.WindowEnd();
}

Found an issue with these docs, or have some additional questions? Create an Issue on Github!