Dear all,
I’m working with qgis 3.4. This is my first Qgis modeler. I’m facing to an error message during the running of the modeler. If i understand the error message, the error seems to occur during the step “D” on my little screenshot (below) showing the modeler.For information, i’ve defined a conditional branch. In addition to the screenshot of the modeler, i paste also the error message.
Modeler explanation :
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The output of the algorithm A is a raster clipped with a polygon (an area of interest)
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For the algorithm B (difference vector processing between 2 input layers), I’ve setted a dependency so that it only triggers if a condition is met (we can see the conditional branch ‘C’ on the screenshot).
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Algorithm D (clip raster with a polygon) takes as input the raster output/result of the algorithm A. And as a mask layer, the vector result of algorithm B (difference). For this algorithm D, I’ve still enable the same dependency setted for the algorithm B.
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For algorithm E (raster polygonization),we can see there are 2 possible raster inputs. The output of the algorithm A and the output of the algorithm D. Thus, as input to algorithm E, I set the following expression (pre-calculated value):
if (@exclude_forest_zones , @cut_raster_segmentation_by_mask_vector_NO_foret_OUTPUT , @cut_raster_segmentation_by_study_area_vector_OUTPUT)
When I run the modeler, I get an error message that seems to be related to algorithm D. Below is the error message:
"Unable to evaluate the expression for the extra parameter to clip the raster segmentation by the NO forest mask: no root node! Execution failed after 8 seconds."
For information, i paste below the overview of the algorithm D :
And i paste below for information the overview of the algorithm E : As you can see on the screenshot, I haven’t defined any dependencies for algorithm this algo E :
Thanks so much for your usefull and valuable help.