Textures are a 2 dimensional image, projected and scaled as needed. The process can be complicated, so we’ve outlined a process for preparing 2 dimensional images, as well as positioning them as UV maps.
Correcting Perspective #
In order to reduce model size while simultaneously displaying realistic textures, we can use photos of real buildings on our models, eliminating the need to model every vertex. Because of the distance at which photos of buildings can be taken, this means that photos are taken in perspective, which must be changed to an isometric view (straight-on and without perspective) in order to create a realistic texture. NOTE: Photos from directly in front of the building make the task much easier.
The first task is adding guidelines to ensure the photo is as square as possible. Turn on rulers under View- Rulers.
Click onto the rulers (1) and drag guidelines onto the photo to roughly where they are needed.
With the guidelines arranged in a box, we can begin correcting the perspective. choose Edit- Transform- Perspective.
A box appears around the photo. Click on the control points in the corner and drag outwards.
Perspective can be almost completely controlled via the Transform- perspective operation. However, if the photo is now warped, it may be necessary to warp the photo to fit the new isometric view. This should be used at the end as a fine adjustment.
The background is not needed for the texture. Resize the photo (Ctrl + T) and use the Lasso tool to remove the bulk of the background.
With the background removed, fit the photo back into the guides. Once the building fits perfectly into the guides, use the lasso tool on the guides to remove any remaining background
The building is actually much taller than the photo shows, which needs to be corrected. Using transform (Ctrl + T), pull the top of the photo upwards until it looks correct. If the exact dimensions of the building are known, it is possible to use the ruler to scale it to the correct size, though this is not really necessary as long as the dimensions are roughly the same.
Once this process is done for all sides, they can be added together side by side. Correct any size differences and crop the image using the crop tool on the toolbar. One texture file will make the UV Mapping easier. Only three sides are used here in order to better explain UV Mapping.
When saving, reduce the file quality to reduce it’s size.
UV Mapping #
To import the texture onto a Blender model, we need to switch to the shading tab on the top toolbar. To add a new material, click on the “+” sign on the right under the material properties tab (1), then click the “New Material” button (2). This will generate new nodes below (see next image).
A principled BSDF and material output node should have appeared in the material field. We need to add a texture node to import the new texture. Go to Add- texture- image texture, and import the new texture. Add the join the “Colour” on the image texture to the “Base Colour” on the Principled BSDF. You can also select the existing texture and add the node and texture there.
The texture will import completely out of scale and often rotated 90 degrees. To correct this, we need to use the UV Mapping tab. To have Blender project the new texture in 2D in the UV Mapping tab, we need to first select the entire object (A) in edit mode, press “U” and then choose “Unwrap”. This takes the model and lays it out flat, like the way a cardboard box looks when layed flat. This makes it easier to position the textures accurately.
On the left you can see the model unwrapped. This is the reason the textures are so distorted on the model- the UVs are not yet correctly positioned on the left.
Choosing a single face on the model will display that UV on the left- the UV can be understood as a window- whatever is seen through the window will be shown on the model. It is now a simple matter of selecting the vertices, vertexes or faces on the left, and moving it to fit. It can also be scaled to fit, or two corners can be selected and moved into place as desired. Tip– after pressing “G” to move the vertices, lock them to the x,y, and z axis by pushing x,y,or z. This will keep the UV square.
The texture was also imported rotated in relation to the model. Select all the vertices and rotate (R) 90 degrees (after pressing R, press 90, or -90 and then enter). Then reposition the vertices again to fit. The fourth side can use any of the existing textures.
The model is ready for any additional effects. The roof can be sampled by a section of the walls that don’t have windows, since the roof is will not be a point of focus. Alternatively, another material can be applied and another texture loaded.