petrel tips&tricks from scm, inc. · pdf filepetrel is a mark of schlumberger 4801 woodway...

Petrel is a mark of Schlumberger

4801 Woodway Drive, Suite 150W • Houston, TX 77056 • www.scminc.com • [email protected]

Copyright © 2000-2009 SCM, Inc. – All Rights Reserved

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K n o w l e d g e W o r t h S h a r i n g

Petrel TIPS&TRICKS from SCM, Inc.

Make It Snow Workflow Man has dreamed of controlling the weather since before fire and before the wheel. Now, with Petrel, man can achieve this goal. Using a Petrel Workflow we have made it snow in a window seen in 3D space. Granted, this is a small step for mankind, but as a Petrel user this could be a giant leap forward in your workflow knowledge. This Petrel TIPS&TRICKS walks you through the loops and methods needed to simulate falling snow. Imagine telling your family and friends during the Holiday parties that you were able to make it snow. You will be the talk of the party!

Figure: Logical flow in the evolution of human technology.

This Snowfall workflow uses a single loop and a nested pair of loops to make it snow. There are no special tricks (other than random number generation) being used and no exotic processes being executed. For that reason this workflow makes an excellent TIPS&TRICKS example. The following discussion will walk you through the logic and design of the workflow.

Design

The general design of any workflow should be planned before starting to build it. The authors normally do this using an outline and/or a series of sketches (these are presented in figures in the section below). Once the plan is finished workflow construction begins. This same approach was used for the Snowfall workflow.

Fire Wheel Petrel Make Snow




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Skeleton Workflow

First a skeleton workflow telling what is happening at each step is created. This workflow contains messages and comments and any logic required to make the workflow execute. When executed, the Skeleton workflow will write an outline of the processing steps to the Petrel message log.

Once the Skeleton workflow is working correctly then the executable commands are slowly added using proper QC along the way. This slow enhancement continues until the workflow is complete and the results correct.

Figure: Skeleton workflow containing only logic and messages to indicate whether the design works correctly.




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Figure: Message log generated by the Skeleton workflow.

Logic and Processing Steps

The input and steps required to make it snow in Petrel are outlined in the figures below. Following each figure(s) is the completed portion of the workflow that performs that function.

User Input to Workflow

Input that the user provides the workflow includes:

Polygon representing the snowflake

X‐Y limits of the snowfall area

Number of flakes

Number of times to shift the flakes downward

Distance to shift the flake downward (the larger this distance the faster the flake moves)

Figure: The User uses Make/edit Polygons to create a snowflake (left) and defines the X‐Y limits of the Snow area (right). Both are entered into the workflow. Note the original snowflake (blue star) is not in the




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area; its location can be anywhere. The snow flake and snow area should be sized so that the flake and its detail are easily seen when displayed in the snow area.

Figure: The User specifies, as input to the workflow, the number of snow flakes to be made, distance each flake should fall (shift increment), and number of times each flake should fall (be shifted downward). Note the dashed line represents the snow area with a flake starting in a random position and being shifted down and out of the area by equal shift increments.

Number of flakes

Fall distance (shift increment)

Snow Area

Xmin = 0

Xmax = 3700

Ymin = 1000

Ymax = 6000

Number of falls (shifts)




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Figure: Portion of the Workflow used to input files folders and parameters.




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Create Seed Snowflake

To make it easy for the program to create many snowflakes it needs to have one flake in a known X‐Y position. The original input flake is copied and the copy is named and moved to the lower left corner of the snow area. This copied flake becomes the seed for creating all snowflakes used by the workflow.

Figure: The Workflow makes a copy of the snow flake, determines its min‐X and min‐Y position, calculates the shifts needed to get it to Xmin and Ymin of the Snow area, and translates the copied flake to lower left corner of Snow area.

Figure: Portion of the Workflow used to create and position the seed snowflake.

Dy

Dx




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Create Snowflakes

The snowflakes are created by copying the seed flake and then randomly positioning the copies in the snow area. Each copy is then resized, made to appear rotated and given a color.

Figure: The Workflow randomly picks a value between 0 and X‐range of the snow area and another between 0 and Y‐range of the area and shifts a copy of the seed snowflake by those values, it randomly resizes the shifted flake (using a multiplier between 1 and 3), it randomly rotates the flake (scales X by random number between .4 and 1.0 and similarly Y), and it randomly colors the flake (assigns a random Z between 0 and 300 to the flake, with the color table setting the color).

Figure: Portion of the Workflow used to create the snowflakes and place them randomly in the snow area.

Dy

Dx

Randomly position copy in snow area

Randomly resize snow flake

Randomly rotate snow flake

Randomly shift Z of snow flake (color)




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Delete Seed Flake

Once the snowflakes are built the seed snowflake is no longer needed.

Figure: Portion of the Workflow used to delete the seed snowflake.

Make Snow Fall

The snowflakes that have been placed in the snow area are made to fall by shifting each flake down (in the Y direction) by the shift increment. This is done as many times as was specified in the input parameters.

Figure: The snowflakes are all shifted one increment down and then the shift process is repeated. This gives the illusion of the snow falling. Cartoon example of one flake being shifted (left) and several being shifted (right).

One snowflake shifted many times

All snowflakes shifted many times




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Figure: Portion of the Workflow used shift the snowflakes downward (make it snow).

Final Display

To add “realism” to the display a window was created using polygons. A series of lines were created that looked like the sill and outline of the pains in a window. These window polygons were located over an area just below the snow area (south). This allowed the snow to be created by the workflow and then to pass behind (outside) the window as the flakes moved downward.




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Figure: Window with snow falling “outside”.

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