# (9) Flying over the Antarctic Ridge and the East Pacific Rise

Animation of a simulated fly-over of the Pacific basin mid-ocean ridge system. It uses a premade flight path that originally was derived from a data file of the world’s ridges, then filtered and manipulated to give the equidistant path to simulate a constant velocity at the given altitude, with synthetic banking as we turn to follow the path. We use the 30 arc second global relief grid and overlay a few labels for named features.

- Grid: @earth_relief_30s

- Path: MOR_PAC_twist_path.txt

- Labels: MOR_names.txt

We create a global intensity grid using shading from East, a global relief grid and a CPT file; these are created by the preflight script. We add a 1 second fade in and a 1 second fade out for the animation The resulting movie was presented at the Fall 2019 AGU meeting in an eLighting talk: P. Wessel, 2019, GMT science animations for the masses, Abstract IN21B-11.

The finished movie is available in our YouTube channel as well (without fading): https://youtu.be/LTxlR5LuJ8g

The movie took ~6 hours to render on a 24-core MacPro 2013.

    #!/usr/bin/env bash
    #
    # Animation of a simulated fly-over of the Pacific basin mid-ocean ridge system.
    # It uses a premade flight path that originally was derived from a data file
    # of the world's ridges, then filtered and manipulated to give the equidistant
    # path to simulate a constant velocity at the given altitude, with synthetic
    # banking as we turn to follow the path.  We use the 30 arc second global relief
    # grid and overlay a few labels for named features.
    # DEM:   @earth_relief_30s
    # Path:   MOR_PAC_twist_path.txt
    # Labels: MOR_names.txt
    # We create a global intensity grid using shading from East and a CPT file; these are
    # created by the preflight script.
    # We add a 1 second fade in and a 1 second fade out for the animation
    # The resulting movie was presented at the Fall 2019 AGU meeting in an eLighting talk:
    # P. Wessel, 2019, GMT science animations for the masses, Abstract IN21B-11.
    # The finished movie is available in our YouTube channel as well (without fading):
    # https://youtu.be/LTxlR5LuJ8g
    # The movie took ~2 hours to render on a 10-core M1 MacBook Pro 2021.

    # 0. A set of parameters needed by all frames
    cat << 'EOF' > inc.sh
    ALTITUDE=1000
    TILT=55
    WIDTH=36
    HEIGHT=34
    EOF
    # 1. Pre-script: Runs once to produce files needed for all frames
    cat << 'EOF' > pre.sh
    #!/usr/bin/env bash
    gmt begin
    	gmt grdcut -Rd @earth_relief_30s -Gearth_relief_30s.nc
    	gmt grdgradient earth_relief_30s.nc -A90 -Nt2.5 -Gearth_relief_30s+2.5_int.nc
    	gmt makecpt -Cgeo -H > MOR_topo.cpt
    gmt end
    EOF
    # 2. Main frame script that makes a single frame given the location and twist from the data file
    # and the other view parameters from the include file.
    cat << 'EOF' > main.sh
    #!/usr/bin/env bash
    gmt begin
    	gmt grdimage -Rg -JG${MOVIE_COL0}/${MOVIE_COL1}/${MOVIE_WIDTH}+z${ALTITUDE}+a${MOVIE_COL2}+t${TILT}+w${MOVIE_COL3}+v${WIDTH}/${HEIGHT} \
    	  -Y0 -X0 earth_relief_30s.nc -Iearth_relief_30s+2.5_int.nc -CMOR_topo.cpt
    	gmt events MOR_names.txt -L100 -Et+r6+f6 -T${MOVIE_FRAME} -F+f12p,Helvetica-Bold,yellow
    gmt end
    EOF
    # 3. Run the movie
    gmt set PROJ_LENGTH_UNIT inch FONT_TAG 20p,Helvetica,white
    gmt movie main.sh -Iinc.sh -CHD -Sbpre.sh -TMOR_PAC_twist_path.txt -Nanim09 -D24 -H4 -K -M2000,png -Fmp4 -Gblack -Le+jTR -Lf -V -W -Zs
    rm -f gmt.conf