Compile an Occlusion-Roughness-MEtallic map from individual images as per "Art Pipeline for glTF" https://www.khronos.org/blog/art-pipeline-for-gltf

makefile

SHELL=/bin/bash

help:
	@grep -E '^[a-zA-Z_-%]+:.*?## .*$$' $(MAKEFILE_LIST) | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-20s\033[0m %s\n", $$1, $$2}'
### https://www.digitalocean.com/community/tutorials/how-to-use-makefiles-to-automate-repetitive-tasks-on-an-ubuntu-vps

%_orm.png: %_*.png ## Make a glTF-compliant Occlusion-Roughness-Metallic map from individual files named accordingly
	@if [ -f '$*_occlusion.png' ] ; then \
		FILER="$*_occlusion.png"; CHANNELR="R"; \
		echo "Found $$FILER --> $$CHANNELR"; \
	elif [ -f '$*_ao.png' ] ; then \
		FILER="$*_ao.png"; CHANNELR="R"; \
		echo "Found $$FILER --> $$CHANNELR"; \
	else \
		echo "occlusion will be missing in $@"; \
	fi; \
	if [ ! -f '$*_roughness.png' ] ; then \
		echo "roughness will be missing in $@"; \
	else \
		FILEG="$*_roughness.png"; CHANNELG="G"; \
		echo "Found $$FILEG --> $$CHANNELG"; \
	fi; \
	if [ ! -f '$*_metallic.png' ] ; then \
		echo "metallic will be missing in $@"; \
	else \
		FILEG="$*_metallic.png"; CHANNELB="B"; \
		echo "Found $$FILEB --> $$CHANNELB"; \
	fi; \
	echo "Files found: $$FILER $$FILEG $$FILEB"; \
	echo "Channels used: $$CHANNELR $$CHANNELG $$CHANNELB"; \
	convert $$FILER $$FILEG $$FILEB -background black -channel $$CHANNELR$$CHANNELG$$CHANNELB -combine $@
	@echo "$@ created"
	cp $@ DEPLOY/asset/