The display problem of gltf model with transparent map

3D model with transparency map , Will involve when displaying , According to the transparency on the picture , To display irregular shapes , When making a 3D model , Regular shapes are imported , A rectangle or square , If transparency is not processed , The result displayed is incorrect , For example, the 3D model settings of the trees below ：

Processing software through model , Set the material （material） Properties of , When the model can be displayed in the engine , The transparent position is not displayed , So as to achieve the correct display mode ：

The specific way of operation is before the official account. ：Blender Export with transparency map gltf Model

In practice , 3D model with multiple maps , It will be slow to modify attribute information one by one , have access to Blender Medium python Batch modification of scripts , See official account. ：Blender Script development , attach ： How to modify the properties of all materials in a model （material） Of python Code ：
//bpy.data Model data in the scene
materials = bpy.data.materials
for (k1,v1) in materials.items():
v1.blend_method = ‘BLEND’

Set the exported 3D model in this way , Set the materials to BLEND attribute , When the material in the model has transparent channels （ for example png Format ）, stay three.js perhaps cesium When displayed in the , There will be the problem of mixing with the background , The model display penetrates the background , Here's the picture ：

Material without transparent channel , for example jpg Format , Can avoid such problems , therefore , When setting the map of the model , According to different situations , Set different properties , stay gltf Model format description , You can also set the transparency property of the model to mask, This can also avoid such problems .
attach gltf Description of model material parameter settings （blend and mask）：
MASK - The rendered output is either fully opaque or fully transparent depending on the alpha value and the specified alpha cutoff value; the exact appearance of the edges MAY be subject to implementation-specific techniques such as “Alpha-to-Coverage”.
BLEND - The rendered output is combined with the background using the “over” operator as described in Compositing digital images.