<cat>Code.Misc</cat>⤶ <cat>Code.Game</cat>⤶ <title>Traces</title> # What are traces Traces are imaginary lines. When you run a Trace you get a TraceResult - which tells you what the line hit. So for example, if you, as the player, wanted to spawn a box. You'd run a Trace from the player's eyeball to 200 units in the direction that the player is looking. The TraceResult would show that it hit a point and now you know where to place the box. <upload src="a61e9/8d9152587ef3390.png" size="16905" name="image.png" /> # Tracing Traces are constructed using the Trace static functions, and configured using members. You run the trace and get the result using Run(). ``` var mytrace = Trace.Ray( startPos, endPos ); mytrace = mytrace.WorldOnly(); var result = mytrace.Run(); ``` The configuration functions return a new object. This is a convenience thing, so you can format like this: ``` var tr = Trace.Ray( startPos, endPos ).Run(); ``` or like this ``` var tr = Trace.Ray( startPos, endPos ) .Ignore( playerEntity ) .Ignore( playerVehicle ) .Size( 10 ) .Run(); ``` ## Size In the example above the Size describes the size of an AABB to trace. This means instead of tracing a simple line, you're tracing a bigger cube along the line. ## RunAll Instead of ending your Trace with ```Run()``` function, you can use the ```RunAll()``` function. Using RunAll will tell your Trace that you don't want to stop at the first entity who's been hit. Instead it'll return an array containing a TraceResult for each entity that was hit along the path of the trace. An example use case for this function would be for bullets that penetrate through objects. ``` // Will return TraceResult[] that you can iterate over var tr = Trace.Ray( startPos, endPos ) .RunAll(); ``` # TraceResult The Trace Result is a simple struct. It gives you information on the hit. Here you can see testing whether the trace hit and using the hit position to spawn an entity 10 units above it. ``` if ( tr.Hit ) { var ent = new ModelEntity(); ent.SetModel( "models/sbox_props/watermelon/watermelon.vmdl" ); ent.Pos = tr.EndPos + tr.Normal * 10; } ``` # TODO Explain how to trace using other shapes