Once you have a model, carry out the following steps to decimate your model:
Part 1
- First using Photoshop or gimp, reduce your file size.
- Go into textures - reduce the size of the images one by one (don't go too small)
- After you scale down, override for each image
- Use GLtf to GLB Packer https://glb-packer.glitch.me/ - which compresses all the things into one file
Part 2
In Blender:
- Open your GLB in Blender (delete the default cube first)
- Click through the model hierarchy on the right till you see a green mesh icon, select the "parent" (one above the green), go to object mode & select all, CTRL J (while mouse in the 3d View) to join all the bits
- Below green icon push CTRL B to select the rest of the hierarchy and click delete hierarchy
- Then Go to Edit mode > Mesh > Merge by distance - the larger the distance the smaller you are making the model but watch out for distortion
- Zoom in on detailed areas and merge there to simplify further
- Export as GLB
(Blender is a free 3D computer graphics software)
Reduce texture size
- This is the most important for file size and avoiding app crashes.
- First using Photoshop or gimp, reduce your file size.
- Go into textures - reduce the size of the images one by one (don't go too small)
- After you scale down, override for each image.
- If you can use Blender, save textures .jpg instead of png, tiff or tga to reduce the size and replace textures.
- Use GLtf to GLB Packer https://glb-packer.glitch.me/ - which compresses all the things into one file
Reduce object count
- This is the most important for performance.
- Import your model in Blender.
- Press F3 and type ‘select linked material’ and click. (Keyboard shortcut is Shift+L)
- Objects that have the same material are selected.
- Press F3 and type ‘join’ and click. (Keyboard shortcut is Control+J)
- Repeat 2~4 until the objects are merged by material.
Reduce vertex count
- This is important to reduce file size and improve performance.
- Select an object that you want to reduce vertex count.
- Merge vertices. (This could cause smoothen edges)
2-1. Go to ‘Edit Mode’ by pressing the ‘tab’ key. (Or clicking ‘Object Mode’ box on the left-top)
2-2. Press ‘1’ to vertex mode and ‘A’ to select all vertices.
2-3. Press F3 and type ‘merge by distance’ and click. (Keyboard shortcut is M and select ‘By Distance’)
2-3. Press ‘tab’ again to go back to the ‘Object Mode’. - Reduce vertex count using Decimate Modifier.
3-1. Go to ‘Modifier Property’ on the right menu.
3-2. Click ‘Add Modifier’ and select ‘Decimate’.
3-3. Change ‘Ratio’ number like 0.5.
3-4. Hover your mouse cursor on the modifier and press ‘Ctrl+A’ to apply it. - Repeat 1~3 until you reduce vertices of all objects.