This is actually going to be really simple.......honest!
Open a new transparent image, 600x400. Add a new layer called Middle Wall. Set your top Styles swatch to the solid color that is middle gray. Click on your Selection tool and select an area on your 600x400 image similar to what is shown below. You will be adding a left and right wall, a ceiling and a floor. When you make this selection, keep all that in mind. You want more floor space available than ceiling space. Now floodfill your selection with the middle gray solid color.
Add a new layer called Left Wall. Change the solid color to light gray. With the Selection tool, make a selection similar to the one below. You want to select from the middle wall over to the edge of the image area. Make this selection about 50 pixels longer than the middle wall. Making this selection shorter or longer will define the degree of angle your room will have.
Click on the Deform tool. Hold down the Ctrl key on the keyboard. Place your cursor on either the top or the bottom of the right side of the left wall. Now push inward while holding down the Ctrl key and the left mouse click. See the square blocks that are meeting the middle wall? You want the top and bottom blocks to match up on the same line as the top and bottom line of the middle wall. After you have Deformed the left wall so that the right side meets the middle wall, you can zoom in and see how well they meet. If you are off, then click on the Deform tool again and either push the wall straight down until they match or pull it up until they match.
Once your left wall is done, copy and paste it as a new layer, Right Wall. Mirror the layer.
This is how your image should look now.
Change the top Styles swatch to the solid color white. Add a new layer called Floor. Make a selection along the bottom of your image similar to the one below. Make sure you have selected above the bottom of the walls. Now flood fill with the white. Add a new layer called Ceiling. Make a selection like you did for the floor. Flood fill with the white. The Floor and the Ceiling layers need to be below/under the wall layers.
This is now how your basic room should look. If you haven't saved the file yet, save it as template or room_template.psp. Make a copy of the file to work on.
Make your Ceiling layer active. Change the top Styles swatch
to the Pattern Spatch.
Change the Scale to 50. Flood fill with
the Spatch Pattern.
Make your Floor layer active. Change the Pattern
to Pine. Set the Scale to 25.
Flood fill the Floor layer with the Pine Pattern.
Well.......you've got your floor and ceiling done before the walls!
