Gizmo clipping plane fix (playcanvas#7045)

* clamped z to w to prevent clipping

* fixed z clamping issue with cull flag

* Updated get selection to use camera position and screen to world with clip range

* Removed sign from gizmo shader

src/extras/gizmo/gizmo.js

@@ -461,8 +461,8 @@ class Gizmo extends EventHandler {
      * @private
      */
     _getSelection(x, y) {
-        const start = this._camera.screenToWorld(x, y, this._camera.nearClip);
-        const end = this._camera.screenToWorld(x, y, this._camera.farClip);
+        const start = this._camera.entity.getPosition();
+        const end = this._camera.screenToWorld(x, y, this._camera.farClip - this._camera.nearClip);
         const dir = end.clone().sub(start).normalize();
 
         const selection = [];

src/extras/gizmo/shape/shape.js

@@ -48,18 +48,17 @@ const shaderDesc = {
         attribute vec3 vertex_position;
         attribute vec4 vertex_color;
         varying vec4 vColor;
-        varying vec2 vZW;
         uniform mat4 matrix_model;
         uniform mat4 matrix_viewProjection;
         void main(void) {
             gl_Position = matrix_viewProjection * matrix_model * vec4(vertex_position, 1.0);
+            gl_Position.z = clamp(gl_Position.z, -abs(gl_Position.w), abs(gl_Position.w));
             vColor = vertex_color;
         }
     `,
     fragmentCode: /* glsl */`
         precision highp float;
         varying vec4 vColor;
-        varying vec2 vZW;
         void main(void) {
             gl_FragColor = vColor;
         }
@@ -308,6 +307,7 @@ class Shape {
         const meshInstances = [];
         for (let i = 0; i < meshes.length; i++) {
             const mi = new MeshInstance(meshes[i], material);
+            mi.cull = false;
             meshInstances.push(mi);
             this.meshInstances.push(mi);
         }