[flow_default] Transcription: 01_image-based_lighting_02.json

transcriptions/01_image-based_lighting_02.json

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+{
+  "audio_file": "01_image-based_lighting_02.wav",
+  "text": "What is image-based lighting? As its name implies, it's the lighting technique that takes color from the image pixels, be it a photo or a video, and emits that color onto a 3D scene. To start playing with that technique, we need a surface to map our image texture to. Like a plane, for example. But first, the plan. The plan is such that our goal is to make it a backlight that pushes the color from that direction and generally any direction that is a background direction if that makes sense. It is rather simple. We just want it to be a backlight kind of thing. Or the reverse key lighting if you watched that tutorial on our channel. Okay, with that out of the way, now we can add a plane. As usual for every new light layer I'll be creating a new collection. Right click, HGRI background. Now I will go Shift A to add a mesh plane. It will be a holder of a photo used as a light source. All the material settings for the light materials as well are set in the shader editor. So why don't we open it right away? The mode should be set to object, not world. Now I'll click on you to add a new material. This is going to be a HGRI background underscore 01 in the object name as well. We can get rid of the principled BSDF shader I think. So right-click and delete it for good. And right away shift a texture, image texture. If we feed its color into the material surface input we'll see magenta light emanating from the plane's surface. That's because by default Blender adds Magenta if the texture is missing. Actually, plugging texture right into the surface input like that is the same as adding the emission shader first. The same thing. It just creates one under the hood. So we'd better deeper. To add a texture, click Open and go to the Image folder with the images. You can find it in the Tutorial Resources, by the way. There is a bunch of night city photos from Pixabay here, licensed under Publix. Okay, can you guess the one that I G to move, R to rotate, S to scale. X, Y and Z to control the axis. The basic controls for movement and blender. For example, R and Z constrain the rotation to the Z axis like that. R and Y to the Y and Z to the Z axis. very useful to know I'm sure you know because the original photo wasn't square. Now we can preview it from our camera perspective by hitting zero on the NOMpad. It looks okay. I'll just fine-tune the placement, the scale and the width and it should be fine. Extending Dynamic Range In this section we'll take our 8-bit JPEG and extend its Dynamic Range in Blender's shader editor. This will turn it into an HDR image, which is good for lighting. So the issue with the regular JPEGs and stuff like that is that by default their range of intensities isn't impressive. If you reduce the emission strength you'll see there are no bright spots left, no areas of higher intensity. In other words, the night sky has an okay intensity as for now probably. It can be rather dark after all, but the neon light should still retain their power even after reducing the overall exposure. And say, if you bring the strength way up to give these lights a proper exposure, by that time you'll have a blown out sky. No longer in the lower range, not looking like night at all. There's just too little contrast or too little range to the source image. To prove it with numbers, let's render this frame out. Let's go render, render image. Once it's rendered, I'll expand the image viewer by holding CTRL and hitting SPACE to make it nice and big. And now let's sample, let's say the blacks on the hoodie first with control right-clicking on these pixels. Control and right-clicking, okay? What do you see? There is no light at all hitting this part of the image, so the RGB values read out at the bottom of the screen should now show zeros or nearly zero in both red, green and blue channels. The left column shows the scene referred values while the right the RGB values after preparing it for display both showing zero intensity now let's do the second readout but for the blue sky pixels in the upper left corner this time control right click let me zoom out the values for you and now we can see that there is some intensity in these values, mostly in the blue channel and surprisingly, it's a blue sky after all. Still, it's a very low amount of light, 0.0 something, which makes sense. Now let's check the readout of these yellow neon lights, which are currently not yellow at all, just this moody shade of military brown. The Sin-Referred Light values are still really weak. 0.01 something. It's almost the same light strength as the night sky, which is quite absurd and worth a scandal. The intuition tells it should be many thousand times more powerful, right? Now, once we measured it in absolute values, we can extend the dynamic range of the source image so these parts get as hot as they deserve to be.",
+  "language": "en",
+  "confidence": null,
+  "duration": 495.94
+}