Hello, this is the first time to post here.

When I render Fire simulation, I cannot find the fire mask.
I want to make alpha so that I take that rgb and alpha image to NUKE for compositing color, brightness and so on.

But the alpha image has only smoke, not fire or flame.
How can I make the matte for fire..?
I use Houdini15.
Thanks.

There are quite a few exports available from the Pyro v3 shader.

The two that you can use to generate just the fire element are vector all_emission and vector Ce for Color Emission (which is in most shaders).

There is also vector direct_emission and vector indirect_emission.


To export a variable, just go to the Mantra ROP Output Driver and in the extra image planes tab, create a new export and make sure to set both the type and name and enable to see the extra image plane generated.

Here is a grab from the generated vex code from the Pyro v3 shader HDA asset. Many will export nothing depending on the features you are using in the Pyro shader:

export vector direct = { 0, 0, 0 };
export vector indirect = { 0, 0, 0 };
export vector Ce = { 0, 0, 0 };
export vector direct_emission = { 0, 0, 0 };
export vector all_emission = { 0, 0, 0 };
export vector all = { 0, 0, 0 };
export vector indirect_emission = { 0, 0, 0 };
export vector direct_comp = {};
export vector indirect_comp = {};
export vector all_comp = {};
export vector direct_noshadow = { 0, 0, 0 };
export vector direct_shadow = { 0, 0, 0 };
export vector indirect_noshadow = { 0, 0, 0 };
export vector indirect_shadow = { 0, 0, 0 };
export float level = 0;
export float diffuselevel = 0;
export float specularlevel = 0;
export float volumelevel = 0;
export float direct_samples = 0;
export float indirect_samples = 0;
export float nlights = 0;
export vector direct_noshadow_comp = {};
export vector indirect_noshadow_comp = {};


Tip:
I always inspect shader code when finding all exports. Fastest way I know. Beats trolling through vast VOP shader networks.

When using a shader I haven't written, I always RMB (RightMouseButton) on the shader and choose the operation to generate vex code. Then in the pop up window showing all the vex code generated from the network, scroll past all the pragma UI hint statements and included functions to get to the actual shader function call.

In there, you will find a few export declarations for various input parameters (mostly hidden btw). You can generate exports from these variables by name.

or…

Just search for the keyword “export”…

Thank you very much Jeff. I saw your answer few month ago, sorry for replying late.
yeah, I got to know exporting ‘all_emission’, which is what I exactly wanted to get.
I'm not good at VEX code yet. but your tips are very helpful for studying. Thanks!

hey there Thanks
meet same problem in Houdini 17
so found way to export that with Vector4Type working good!

Oh It’s so simple! I will try that in houdini17!! Thanks