Cursor World Position

[jrj996]

Is there a way to retrieve where the cursor would be in the world? Kinda like how the clicker works in sandbox, where if a player right clicks and entity a menu pops up, I'm trying to find out the position of the cursor. The only difference is, is that I'm using a custom view, it's over the top of the player.

I'd appreciate any help!

[seanlaff]

You can use this [url]http://maurits.tv/data/garrysmod/wiki/wiki.garrysmod.com/indexa938.html[/url] which gives you the vector of the cursor poisition. Then I think what I did when I had this problem was take that vector and draw a really long trace along it (like 10000 units) and then return the coordinates of where that trace intersected with the world or an entity.

[jrj996]

Could you give a piece of example code? I don't quite understand what you mean :v: Sorry...

I tried using this old chunk of code from the wiki and from my google results,

[lua]
Give this function the coordinates of a pixel on your screen, and it will return a unit vector pointing
in the direction that the camera would project that pixel in.

Useful for converting mouse positions to aim vectors for traces.

iScreenX is the x position of your cursor on the screen, in pixels.
iScreenY is the y position of your cursor on the screen, in pixels.
iScreenW is the width of the screen, in pixels.
iScreenH is the height of the screen, in pixels.
angCamRot is the angle your camera is at
fFoV is the Field of View (FOV) of your camera in ___radians___
Note: This must be nonzero or you will get a divide by zero error.
--
function LPCameraScreenToVector( iScreenX, iScreenY, iScreenW, iScreenH, angCamRot, fFoV )
--This code works by basically treating the camera like a frustrum of a pyramid.
--We slice this frustrum at a distance "d" from the camera, where the slice will be a rectangle whose width equals the "4:3" width corresponding to the given screen height.
local d = 4 * iScreenH / ( 6 * math.tan( 0.5 * fFoV ) ) ;

--Forward, right, and up vectors (need these to convert from local to world coordinates
local vForward = angCamRot:Forward();
local vRight = angCamRot:Right();
local vUp = angCamRot:Up();

--Then convert vec to proper world coordinates and return it
return ( d * vForward + ( iScreenX - 0.5 * iScreenW ) * vRight + ( 0.5 * iScreenH - iScreenY ) * vUp ):Normalize();
end

Give this function a vector, pointing from the camera to a position in the world,
and it will return the coordinates of a pixel on your screen - this is where the world position would be projected onto your screen.

Useful for finding where things in the world are on your screen (if they are at all).

vDir is a direction vector pointing from the camera to a position in the world
iScreenW is the width of the screen, in pixels.
iScreenH is the height of the screen, in pixels.
angCamRot is the angle your camera is at
fFoV is the Field of View (FOV) of your camera in ___radians___
Note: This must be nonzero or you will get a divide by zero error.

Returns x, y, iVisibility.
x and y are screen coordinates.
iVisibility will be:
1 if the point is visible
0 if the point is in front of the camera, but is not visible
-1 if the point is behind the camera
--
function VectorToLPCameraScreen( vDir, iScreenW, iScreenH, angCamRot, fFoV )
--Same as we did above, we found distance the camera to a rectangular slice of the camera's frustrum, whose width equals the "4:3" width corresponding to the given screen height.
local d = 4 * iScreenH / ( 6 * math.tan( 0.5 * fFoV ) );
local fdp = angCamRot:Forward():Dot( vDir );

--fdp must be nonzero ( in other words, vDir must not be perpendicular to angCamRot:Forward() )
--or we will get a divide by zero error when calculating vProj below.
if fdp == 0 then
return 0, 0, -1
end

--Using linear projection, project this vector onto the plane of the slice
local vProj = ( d / fdp ) * vDir;

--Dotting the projected vector onto the right and up vectors gives us screen positions relative to the center of the screen.
--We add half-widths / half-heights to these coordinates to give us screen positions relative to the upper-left corner of the screen.
--We have to subtract from the "up" instead of adding, since screen coordinates decrease as they go upwards.
local x = 0.5 * iScreenW + angCamRot:Right():Dot( vProj );
local y = 0.5 * iScreenH - angCamRot:Up():Dot( vProj );

--Lastly we have to ensure these screen positions are actually on the screen.
local iVisibility
if fdp < 0 then --Simple check to see if the object is in front of the camera
iVisibility = -1;
elseif x < 0 || x > iScreenW || y < 0 || y > iScreenH then --We've already determined the object is in front of us, but it may be lurking just outside our field of vision.
iVisibility = 0;
else
iVisibility = 1;
end

return x, y, iVisibility;
end
[/lua]

No luck, the first function, that being the LPCameraScreenToVector function, didn't work at all for me. Won't even return a vector.

[seanlaff]

You need a calcview hook (which is called every frame) to call a function that contains your pointer to world coordinate code. Something like

hook.Add("CalcView", "IsoCam", IsoCam)

IsoCam was the name of the function in my code you can name yours whatever. Then within IsoCam I had

local pointertoworld = gui.ScreenToVector( gui.MouseX(), gui.MouseY() ) // gives us the vector from the cursor to the world
local tracetospace = util.QuickTrace( view.origin, pointertoworld * 10000, ply ) //creates a really long trace from the origin view along the vector we just got

Then just find where that long trace hits the world or an ent and you'll have the coordinates of where the mouse pointer is clicking.