When you are building a composite image, you have to ensure that each of the objects in your composite have a perspective that matches the image into which they are being placed. In this tutorial, we’re going to talk about how to find the horizon of your image and then how to find the vanishing point of objects you drag into your background and then how to line the objects up along the horizon and match the perspective of both the background image and the element dragged into the photo. We’re using two different cars for this example, but this technique works for people, buildings, animals, still life, and more. Once you know it, you’ll love it!
1. How to Find the Horizon Line
Often you will be able to actually see the horizon in your image, but sometimes you need to rely on pre-existing lines in your photo, or even take an educated guess (if the camera angle seems to be pointed down a little, the horizon is in the top half of the image, if the camera is pointed upward a little, the horizon line is in the bottom half of the image.)
2. Working with the Image to Draw the Horizon Line
You can also draw lines off of existing straight-edged objects to create one or two vanishing points. The straight line between these vanishing points is the horizon line. I dropped dots at the vanishing points and then dragged a line between the lines. Photo used in this example: https://unsplash.com/photos/wOeBLz78vGw
3. Find the Vanishing Point of the Car
To get the vanishing point of a car, we can drag out lines off the top and bottom of the wheels and drag them out all the way until the lines meet up. This is the vanishing point of the car image.
4. Finding the Right Place for the Car
To find where the car should go, you simply want to line up the vanishing point of the car with the horizon line. Check out my screenshot to see exactly what I did. TIP: You can move the car wherever it needs to go as long as you’re just dragging it side-to-side. It will remain at the proper perspective.
5. Resizing the Object in Perspective
To resize the object in perspective, you want to Cmd/Ctrl-click the car layer and both of the perspective lines coming off the car in the Layers panel to select all three layers and then hit Cmd/Ctrl + T. Then drag the center anchor point (free transform reference point) over to where the vanishing point touches the horizon line. Hold down Shift + Alt/Opt and scale the Free Transform box bigger or smaller and your car will grow or shrink in size and in perspective. Adjust the car side-to-side to make sure it’s sitting on the road.
6. Doing it all again
I apply this process to a second car in the video just to show you that it does work with any image or object that you may drag into the fray. Find the vanishing point of your object and you can make it work with your composite. NOTE: Some images will never work together on account of the fact that the perspective is SO different between the object and the background images.
7. But, But! What if I need to composite a person, not a car!?
This I did not cover in video, but here is a short explanation and screenshot(s) to help you sort out exactly what to do. When moving a person or an object to a new background, I like to find objects in the photo (where you can) that have straight lines. Use two of those lines and drag out lines that eventually join as we learned above and then cut out the person/object and select that layer as well as the perspective lines and drag that into your background document. Line it all up and scale just like we talked earlier in this post to get a proper perspective. NOTE: If the person’s feet are not visible you do not need to be nearly as concerned with the perspective. DOUBLE NOTE: This is extremely abbreviated and the lighting is different in this background image than in the image of the guy I dragged in so things don’t look “right”, but it’s not because of perspective.
Photo used here: https://unsplash.com/photos/o9yT-NdVHcQ