First Light

Render a sample dataset using Ascent

To start, we run a basic “First Light” example to generate an image. This example renders the an example dataset using ray casting to create a pseudocolor plot. The dataset is one of the built-in Conduit Mesh Blueprint examples, in this case an unstructured mesh composed of hexagons.

C++ Source

#include <iostream>

#include "ascent.hpp"
#include "conduit_blueprint.hpp"

using namespace ascent;
using namespace conduit;

int main(int argc, char **argv)
{
    // echo info about how ascent was configured
    std::cout << ascent::about() << std::endl;

    // create conduit node with an example mesh using 
    // conduit blueprint's braid function
    // ref: https://llnl-conduit.readthedocs.io/en/latest/blueprint_mesh.html#braid

    // things to explore:
    //  changing the mesh resolution

    Node mesh;
    conduit::blueprint::mesh::examples::braid("hexs",
                                              50,
                                              50,
                                              50,
                                              mesh);

    // create an Ascent instance
    Ascent a;

    // open ascent
    a.open();

    // publish mesh data to ascent
    a.publish(mesh);

    //
    // Ascent's interface accepts "actions"
    // that to tell Ascent what to execute
    //
    Node actions;
    Node &add_act = actions.append();
    add_act["action"] = "add_scenes";

    // Create an action that tells Ascent to:
    // add a scene (s1) with one plot (p1)
    // that will render a pseudocolor of 
    // the mesh field `braid`
    Node & scenes = add_act["scenes"];

    // things to explore:
    //  changing plot type (mesh)
    //  changing field name (for this dataset: radial)
    scenes["s1/plots/p1/type"] = "pseudocolor";
    scenes["s1/plots/p1/field"] = "braid";
    // set the output file name (ascent will add ".png")
    scenes["s1/image_name"] = "out_first_light_render_3d";
    
    // view our full actions tree
    std::cout << actions.to_yaml() << std::endl;

    // execute the actions
    a.execute(actions);

    // close ascent
    a.close();
}

Python Source

import conduit
import conduit.blueprint
import ascent

# print details about ascent
print(ascent.about().to_yaml())

# create conduit node with an example mesh using conduit blueprint's braid function
# ref: https://llnl-conduit.readthedocs.io/en/latest/blueprint_mesh.html#braid

# things to explore:
#  changing the mesh resolution

mesh = conduit.Node()
conduit.blueprint.mesh.examples.braid("hexs",
                                      50,
                                      50,
                                      50,
                                      mesh)

# create an Ascent instance
a = ascent.Ascent()

# set options to allow errors propagate to python
ascent_opts = conduit.Node()
ascent_opts["exceptions"] = "forward"

#
# open ascent
#
a.open(ascent_opts)

#
# publish mesh data to ascent
#
a.publish(mesh)

#
# Ascent's interface accepts "actions" 
# that to tell Ascent what to execute
#
actions = conduit.Node()

# Create an action that tells Ascent to:
#  add a scene (s1) with one plot (p1)
#  that will render a pseudocolor of 
#  the mesh field `braid`
add_act = actions.append()
add_act["action"] = "add_scenes"

# declare a scene (s1) and pseudocolor plot (p1)
scenes = add_act["scenes"]

# things to explore:
#  changing plot type (mesh)
#  changing field name (for this dataset: radial)
scenes["s1/plots/p1/type"] = "pseudocolor"
scenes["s1/plots/p1/field"] = "braid"

# set the output file name (ascent will add ".png")
scenes["s1/image_name"] = "out_first_light_render_3d"

# view our full actions tree
print(actions.to_yaml())

# execute the actions
a.execute(actions)

# close ascent
a.close()
_images/out_first_light_render_3d.png

Fig. 27 First Light Example Result