Alpha shouldn't be normalized or inversed? (#704)

* Update simple_viewer.py

* Update gsplat_viewer.py

Author: RongLiu-Leo

examples/gsplat_viewer.py

@@ -21,7 +21,7 @@ class GsplatRenderTabState(RenderTabState):
         "rgb", "depth(accumulated)", "depth(expected)", "alpha"
     ] = "rgb"
     normalize_nearfar: bool = False
-    inverse: bool = True
+    inverse: bool = False
     colormap: Literal[
         "turbo", "viridis", "magma", "inferno", "cividis", "gray"
     ] = "turbo"
@@ -150,12 +150,10 @@ def _(_) -> None:
                 def _(_) -> None:
                     if "depth" in render_mode_dropdown.value:
                         normalize_nearfar_checkbox.disabled = False
+                        inverse_checkbox.disabled = False
                     else:
                         normalize_nearfar_checkbox.disabled = True
-                    if render_mode_dropdown.value == "rgb":
                         inverse_checkbox.disabled = True
-                    else:
-                        inverse_checkbox.disabled = False
                     self.render_tab_state.render_mode = render_mode_dropdown.value
                     self.rerender(_)
 

examples/simple_viewer.py

@@ -197,8 +197,6 @@ def viewer_render_fn(camera_state: CameraState, render_tab_state: RenderTabState
             )
         elif render_tab_state.render_mode == "alpha":
             alpha = render_alphas[0, ..., 0:1]
-            if render_tab_state.inverse:
-                alpha = 1 - alpha
             renders = (
                 apply_float_colormap(alpha, render_tab_state.colormap).cpu().numpy()
             )