Convert from world space coordinate to pixel of render texture

Hey,

I have a scene with a two camera setup. The main camera is perspective, and displays a UI that includes a panel with a render texture (render texture does not take up the entire UI). The Render Texture is created by another camera, which is orthographic, looking down -y, and provides a god's eye view of the world. I have objects in the world and need to take their world position and translate them into screen space positions of the first camera to use for UI buttons, parented to the render texture panel (so that the button positions match the world positions of the objects within the render texture).

Currently I've done:

Vector3 ConvertWorldToScreen( Vector3 positionIn ) {

RectTransform rectTrans = this.GetComponentInParent<RectTransform>();
Vector3 screenCoord = orthoCam.WorldToScreenPoint( positionIn );
Vector3 worldCoord = RectTransformUtility.PixelAdjustPoint( screenCoord, rectTransform.transform, rectTrans.GetComponentInParent<Canvas>() );

Vector2 offset = rectTrans.offsetMin;
return new Vector3( offset.x + worldCoord.x, offset.y + worldCoord.y,1f );​

}

This seems to work but the points are off a bit. I believe they need to be scaled by the same amount the render texture is scaled across the rectangle panel? Not sure if that is correct or how to perform the scaling.

Thanks for any assistance.

 

I've tried scaling by the render texture size:

Vector3 ConvertWorldToScreen( Vector3 positionIn ) {

Texture tex = this.GetComponentInParent<RawImage>();
RectTransform rectTrans = this.GetComponentInParent<RectTransform>();
Rect rect = rectTrans.rect;

Vector3 screenCoord = orthoCam.WorldToScreenPoint( positionIn );
Vector2 scalePoint = new Vector2( ( screenCoord.x * tex.width ) / rec.width, ( screenCoord.y * tex.height ) / rec.height );
Vector2 offset = rectTrans.offsetMin;
return new Vector3( offset.x + scalePoint.x, offset.y + scalePoint.y,1f );​

}

But the location and scaling of the icons from the correct pixel locations is still off.

 

I think I'm close:

Vector3 ConvertWorldToScreen( Vector3 positionIn ) {

RectTransform rectTrans = this.GetComponentInParent<RectTransform>();

Vector2 viewPos = orthercam.WorldToViewportPoint( positionIn );
Vector2 localPos = new Vector2( viewPos.x * rectTrans.sizeDelta.x ), ( viewPos.y * rectTrans.sizeDelta.y ) );
Vector3 worldPos = rectTrans.TransformPoint( localPos );

return new Vector3( worldPos.x, worldPos.y, 1f );​

}

The positions in relation to each other (local positions) are correct, and they are all in the correct x position in relation to the render texture / rectangle panel (world position). The problem I'm having is that the y positions (world positions) are too high, in that they should be near the bottom of the panel but are at the top and above it.

I'm kinda flying by the seat of my pants here, so any input is welcome.

Thanks.

 

http://docs.unity3d.com/ScriptReference/Camera.WorldToScreenPoint.html ?

 

The coordinates are already converted into viewport coordinates. The local and world coordinates I convert from there just get's me their positions within the panel, which is a UI element so it is already in screen coordinates.

 

The solution is to subtract the sizeDelta from the final y coordinate:

Vector3 ConvertWorldToScreen( Vector3 positionIn ) {

RectTransform rectTrans = this.GetComponentInParent<RectTransform>();​

Vector2 viewPos = orthercam.WorldToViewportPoint( positionIn );
Vector2 localPos = new Vector2( viewPos.x * rectTrans.sizeDelta.x ), ( viewPos.y * rectTrans.sizeDelta.y ) );
Vector3 worldPos = rectTrans.TransformPoint( localPos );

return new Vector3( worldPos.x, worldPos.y - rectTrans.sizeDelta.y, 1f );​

}

This threw me off because they still will not line up if you don't have maximize on play enabled, or if your screen resolution is different from your canvas rez. I'm assuming the real problem has to do with aspect ratio, but I don't have time to delve any deeper. If someone wants to enlighten me on why this solution works, I'd be interested to know.

Hope this helps anyone in the future.

 

Hello, so this solution doesn't work if you don't habe maximize on play enabled right or if your screen resolution is different from your canvas resolution, right?

 

Good day

I'm from the future, year 2018. Faced a similar issue, and well.. I wanted it to work with any resolution, and figured a solution that somehow works based on your code.

I figured I'd share it.

public Vector3 ConvertWorldToScreen (Vector3 positionIn)
{
RectTransform rectTrans = this.GetComponentInParent<RectTransform>(); //RenderTextHolder

Vector2 viewPos = otherCam.WorldToViewportPoint (positionIn);
Vector2 localPos = new Vector2 (viewPos.x * rectTrans.sizeDelta.x, viewPos.y * rectTrans.sizeDelta.y);
Vector3 worldPos = rectTrans.TransformPoint (localPos);
float scalerRatio = (1 / this.transform.lossyScale.x) * 2; //Implying all x y z are the same for the lossy scale

return new Vector3 (worldPos.x - rectTrans.sizeDelta.x / scalerRatio, worldPos.y - rectTrans.sizeDelta.y / scalerRatio, 1f);
}

Thankies for sharing your code in the first place, and hope that'll save the life of.. somebody

 

Thanks!

 

Thank you very much! I searched a lot answers but not work. You Save My Life! I think Unity should change the WorldToScreenPoint to your ConvertWorldToScreen solution.

 

Thanks so much for this it's been a huge help! One thing I had trouble with still was getting the UI to work with different screen sizes. To fix this, I took the scaleFactor of the parent canvas and multipled that to the scalerRatio which seems to do the trick! I've added my version below, hope this helps someone!

public Canvas canvasTransform;



    private void Start()

    {



        scaleFactor = canvasTransform.scaleFactor;

    }



    public Vector3 ConvertWorldToScreen(Vector3 positionIn)

    {

        Vector3 viewPos = cam.WorldToViewportPoint(positionIn + offset);

        Vector2 localPos = new Vector2(viewPos.x * rectTrans.rect.width, viewPos.y * rectTrans.rect.height);

        Vector3 worldPos = rectTrans.TransformPoint(localPos);

        float scalerRatio = ((1 / transform.lossyScale.x) * 2) * scaleFactor; 



        return new Vector3(worldPos.x - rectTrans.rect.width / scalerRatio, worldPos.y - rectTrans.rect.height / scalerRatio, 1f);

    }