The Making of Monastery

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This scene is a courtyard in what use to be a monastery. It is now available for the public to wander in, enjoy the solitude, and perhaps read a book. Someone was recently sitting on the pedestal in the foreground reading a paperback book and noticed the way the sunlight was illuminating the stairwell. He stood up momentarily to capture this scene in a photograph.

This was my first ray-tracing attempt, although as I learned techniques while building other scenes I kept coming back to this one to tweak it. I captured the evolution of this scene in the series of pictures below which can be enlarged by clicking on the pictures. I think it illustrates better than any words what is involved in creating scenes like this. The progressive steps on this particular picture is a combination of what would be the normal tweaking of a scene by an experienced ray-tracer and the acquisition of skills as I played with the tool over a number of weeks.

First a slight digression.  The basic tool used in these is Povray.  It is free and you can get your own copy at Povray. Povray is software that traces the path of a ray of light from a light source to an object and out to a camera.  As a user you define the light sources, the objects of the scene and the camera.  You define these in a language that is part of Povray although there are other software tools that will help you create the scene using a point and click environment.  Here is a very simple scene with five objects.  There is a red sphere, a blue box, a plane in Forest Green, plus the light source and the camera.  Povray allows you to define the dimensions, colors and positions of these objects.

You can click on this or any of the other sketches below for a larger view of the picture.

Sphere and Box

There are two things that jump out from this scene. The first is the 3 dimensionality. This is much better than drawing circles and squares on a page. These objects have depth and shadows and it was easy to create this effect. The second thing is that the scene is still very unrealistic. It is plastic, cartoonish. To approach reality you need to add to your scene more complicated shapes, more natural colors, varied surfaces, softer lighting and so on. Povray is amazingly sophisticated and provides the features that allow you to do all of these and much more.

1) The initial effort for the Monastery scene involved the writing of routines to create brick walls arches, and columns. The trick here is to add a degree of randomness to the dimensions, orientation, and color of the bricks. You can also play with the surface texture of the bricks to give them some roughness. While this is a fair amount of effort the routines are reusable in other scenes and in fact the floor tiles in the Monastery are created and laid out with the same routine as the walls.

The next step is laying out the major dimensions, playing with the colors and lighting and finding a good camera angle. As you can see from this early attempt I had a long way to go.

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Notice the randomness in the arch brick dimensions. Not only does the size vary but also the inner radius varies slightly between bricks. This kind of randomness is not easily noticed but if everything is perfectly geometric you will view the scene as unrealistic. Notice also the hard shadows. These needed to be softened.

2) Next I added the stairwell and a potted plant to give the scene some interest. The plant was also created from a general routine that I wrote for creating trees. The tree is just scaled down to fit the pot. The trunk and branches are just series of cones with some spheres placed to smooth the joints between cones. The routine allows you to adjust the probabilities of branching and the amount of randomness allowed in the way the branch wanders. The leaves are also simple shapes that are random in orientation and placed somewhat randomly near the ends of branches.

The pot was created before I tried making any scenes. I was trying to teach myself textures and tried to recreate something I saw in a photograph. The original pot had both white and black lichens growing on it with a considerable amount of dust thrown in the mix. I never did do the original justice and gave up after a while. It looks OK from a distance.

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The stairs were created with the same brick wall routine by adding an ability to offset each brick row. Also the camera angle and aspect ratio was settled by this point.

I spent a large amount of time getting the sunlight in the stairwell the way I wanted. This was tricky. Simple lights just illuminate the wall rather than getting a gradual fading as one moves in toward the courtyard. A simple trial and error process with the Povray parameters on lights gradually improved the effect. As you can see from the scene picture at this stage I still hadn't focused on the overall lighting and color choice.



However, I managed to get rid of the hard shadows by using an "Area Light" that spreads the light source out and more simulates the indirect lighting reflecting off of the sky, or the sky haze rather than direct sunlight.

3) In this next picture the basic scene was coming together. The colors and lighting were about right. Notice the plant changes shape from picture to picture. This is from the randomness in the Tree routine.

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4) This next picture adds a lot of detail. I tapered the column slightly from bottom to top. It is not a cone but has a curve along the height. I created the base and capital of the column. The spiral in the capital is a series of cones with spheres between the cones to smooth out the joints. Each cone is slightly smaller and closer to the center than the one before which creates the spiraling-in effect. You can see this better in the night view of the same scene, Monastery at Night

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I found a picture for an oak leaf on the net. I used Photoshop to trace out the outline of the leaf and make all parts of the picture that was not the leaf transparent. I also adjusted the colors to create a reddish and yellowish version of the original green leaf. Povray allows you to import the leaf picture and I wrapped the leaf picture around a squashed, transparent sphere. This creates a 3D curl to the leaf. I then wrote a routine which randomly orients the leaves and places them somewhat randomly. I focused the leaf placement around the columns as this would tend to be the place leaves blown by the wind would end up.

The book is a simple box with a curved surface placed on top. Povray allows you to define a surface mathematically so I designed an equation that seemed to mimic a curled book cover bound on one side. I imported the picture of the cover of a book I was reading from Amazon and placed it onto this surface.

The door off to the right of the stairwell was added with a light coming from inside the room reflecting off of the door.


5) In the final scene I experimented with the ability to break the floor tiles. One of the tiles between the two foreground pedestals has a substantial chunk missing. I wish the camera angle gave a better view of this because the surface at the break is uneven and jagged like you would get in a real break. Also, on the lower floor and a couple of tiles closer to the camera one of the tiles is cracked.

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I also substantially changed the surface of the bricks on the walls. Rather than having a simple flat surface I defined a routine that generated a random surface on the brick.

I also added a mechanism to place the floor tiles on an uneven ground. If you look carefully you can see this effect but it is subtle and in the end probable not very useful here. I got the idea creating the street for Montemerano where it is used to a much better effect. The uneven floor also forced me to change the mechanism for placing the leaves. Originally they were placed at a fixed elevation. This left them either floating above the floor tiles or partially burried within the tile. The solution was place them a fixed distance off the uneven ground using the same mechanism used to place the tiles themselves.

I also added simple light fixtures to the corridors just off the courtyard which can barely be seen in this daytime picture but allowed me to generate a nighttime version of the same objects by simply adjusting the lighting. I removed the book because the environment was no longer conducive to reading.


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Epilog
A couple of years later I tweaked the scene again. I never did like the tiles which were way too uniform for something built centuries ago. I had perfected the technique for making cobblestones in other images so I replaced the floor with these.

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