Cannot initiate batchsensor with irradiancemeter

[cocoakang]

Hi all,

I want to use a group of irradiancemeters to measure a scene. Iteratively render each meter is time consuming, so I tried to use batch sensor to wrap the irradiancemeters and render the results. However, it seems the batch sensor doesn't think the irradiancemeter as a sensor. I guess because it is wrapped in a Shape object? An example code to reproduce the problem is as below:

import mitsuba as mi
mi.set_variant("cuda_ad_rgb")
  
sensor_dict = {
    "type":"batch",
    "meter_0":{
        "type": "rectangle",
        "sensor": {
            "type": "irradiancemeter",
            "film_0": {
                "type": "hdrfilm",
                "width": 1,
                "height": 1,
                "filter": { "type": "box" }
            }
        },
    }
}

scene = mi.load_dict(sensor_dict)

It will produce this output:

Traceback (most recent call last):
  File "/data/volume1/cocoakang/k.kang/OCT24/cyclops_ir/playground.py", line 20, in <module>
    scene = mi.load_dict(sensor_dict)
RuntimeError: ​[BatchSensor] BatchSensor: at least one child sensor must be specified!

I am wondering if I use the batch sensor in a wrong way. If this feature has not been supported yet, is there any other way to simultaneously measure irradiance of a group of positions? Many thanks in advance!

[leroyvn]

Hi @cocoakang, I'm afraid you're touching on a limitation of this sensor plugin: it is designed to be declared as a child node to the Shape defining the surface on which the incident flux is to be computed; batch expects Sensor child nodes so it won't accept a rectangle (Shape) wrapping an irradiancemeter.

I think this could be addressed by modifying the plugin to accept a shape as an (optional) parameter, opening it to new use cases in the process.

[cocoakang]

Thank you for the quick reply! I will try to modify the code. :)

[njroussel]

👍 I've added this functionnality in 68b8e16 (will be merged onto master soon, currently in #881)