ScreenToWorld / deproject function (Casting a ray into the screen)

[sn1p3ro12]

Been working quite some time on a method to go from a screen location to a location in the world. So I can for example find what my crosshair is pointing at. When I get the time I might implement matrix functions so you no longer need directX. Below is the code I currently use.

What this does

*It takes a pixel on the screen and converts it into a directional vector in world space.
*This directional vector can be used to create a ray
*The ray can in turn be used to find a location in world space
*A good use of this would be to cast a ray from your crosshair


You will need

*DirectX headers and lib linked
*The proper HUD class released by me HERE

D3DXVECTOR3 FVectorToD3DVector(FVector* in)
{
    return D3DXVECTOR3(in->X, in->Y, in->Z);
}

FVector ScreenToWorld(float screenX, float screenY, float screenWidth, float screenHeight,  FMatrix* EngineViewProjection)
{           
            D3DXMATRIX ViewProjection;
            memcpy(&ViewProjection, EngineViewProjection, sizeof(D3DXMATRIX));  //Get the D3D view projection  
        
            D3DXMATRIX View;
            FVector Forward, Up, Right;
            GetAxes(PlayerController->PlayerCamera->Rotation,&Forward, &Right,&Up); // Get where the camera axes are pointing                        
            D3DXMatrixLookAtLH(&View, &D3DXVECTOR3(0,0,0) , &FVectorToD3DVector(&Forward),  &FVectorToD3DVector(&Up)); // Build a D3D view matrix from found up and forward vector

            D3DXMATRIX inverseView;
            D3DXMatrixInverse(&inverseView, NULL, &View); // inverse view matrix
            
            D3DXMATRIX projecti********;
            projecti******** = inverseView * ViewProjection; // calculate the projection matrix NOTE: this only really needs to be done once.             
                
            //Start Ray Calculation
            float w  = screenWidth ;
            float h  = screenHeight;
            
            FVector v;
            v.X =  ( ( ( 2.0f * screenX ) / w  ) - 1 ) / projecti********._11;
            v.Y = -( ( ( 2.0f * screenY ) / h ) - 1 ) / projecti********._22;
            v.Z =  1.0f;
            
            FVector rayDir;
            rayDir.X  = v.X*inverseView._11 + v.Y*inverseView._21 + v.Z*inverseView._31;
            rayDir.Y  = v.X*inverseView._12 + v.Y*inverseView._22 + v.Z*inverseView._32;
            rayDir.Z  = v.X*inverseView._13 + v.Y*inverseView._23 + v.Z*inverseView._33;
            //End Ray Calculation
            
            return rayDir;
}

How to use

Here is how I use it.

        float distance = 10000.0f // 100m
            FVector AimDir = ScreenToWorld( pCanvas->ClipX / 2.0f, pCanvas->ClipY / 2.0f, pCanvas->ClipX, pCanvas->ClipY, &PlayerController->myHUD->m_OldViewProjecti********); // you need to fix the HUD class in the playercontroller or this won't work.
            FVector AimingPoint = PlayerController->PlayerCamera->Location + AimDir *  distance; // create target

Extra info

I am calculating the projection matrix all the time here, you really only need to calculate this once for effeciency, this means you can save on matrix inversions in the future as well
The ******** into the codes means Projection Matrix without the space

Thanks

Credits:
Dogmatt
Fatboy88
EddyK

[ofir001]

I new what I was using it runs the software that anything please help me
need Dev c/C++?

[Margherita]

Nice job, the function of this is pretty interesting

[Eduardkhil]

I don't really mind you re-releasing this here. I mean, if I didn't want the code to be used I would've kept it private. You could've been a little more clear in your post about the fact that you didn't write this though, and put me as the author a little clearer, instead of as a footnote. The same counts for the w2s code that dogmatt wrote. The post reads as if you wrote this.

View O1GKUU.png on ScreenSnapr

[Margherita]

Fixed credits, it was pretty clear, but be more clear next time sn1p

[sn1p3ro12]

Fixed credits, it was pretty clear, but be more clear next time sn1p

Ok bro next time i becarefull thank you !!