Weight painting is the step that decides whether your character bends like a body or folds like a cardboard box. You can have a clean model and a well-built skeleton, and still end up with elbows that collapse and shoulders that tear the moment an animator touches the rig. Most of the work is not painting a whole body by hand. It is fixing Blender's automatic weights at the four or five joints where they always fail, then testing in motion until nothing breaks.
When you bind a mesh to an armature (Blender's word for a skeleton), every vertex needs to know which bones move it and by how much. That information is stored as skin weights. In other software the whole process is called skinning; in Blender you mostly hear it called weight painting, because you edit the weights with a brush.
Each deforming bone has a matching vertex group on the mesh with the same name. A vertex's weight in that group runs from 0 (the bone has no effect) to 1 (the bone moves it completely). In Weight Paint mode Blender shows those values as a heat map: blue is 0, red is 1, and green, yellow and orange sit in between.
A vertex can be influenced by several bones at once. A vertex on the inside of the elbow might be half upper arm and half forearm. That blend is what gives you a smooth bend instead of a hard crease, and getting those blends right is most of the job.
Weight painting cannot fix problems that come from earlier steps. Check these before you pick up the brush:
If modelling, topology and the Blender interface are still new to you, get those basics in place first. The free Blender 3D Bootcamp is a good starting point: six live one-hour sessions over three weeks that take you from the Blender basics through to Unreal Engine, with no experience needed.
Nobody paints a full character from zero. Select the mesh, then Shift-select the armature so it is active, press Ctrl+P and choose With Automatic Weights. Blender creates a vertex group for every deform bone and fills it with a first guess using bone heat, a heat-based estimate of which bone each area of the mesh belongs to.
Automatic weights are a starting point, not a result. They are usually decent along long limbs and poor anywhere bones sit close together: fingers, the armpit, the groin, the neck and the face. Expect to repaint those areas by hand.
If automatic weighting fails with an error, the cause is nearly always the mesh: separate pieces that overlap, duplicate vertices, or a very small scale. Merge by distance, check your scale and try again.
This is the habit that separates clean skinning from endless tweaking. Do not paint a character in its rest pose. You cannot see a bad weight until the joint moves.
Put the armature in Pose Mode and bend the joint you are working on to its extreme: elbow fully bent, arm raised above the head, leg kicked forward, spine twisted. Then, in Object Mode, select the armature, Shift-select the mesh and switch to Weight Paint mode. With both selected you can Ctrl-click a bone in the viewport to make its vertex group the one you paint, and rotate it to test the bend. You can also pick the group from the Vertex Groups list in the mesh's Object Data properties. Either way, you paint and watch the deformation update live.
Better still, key a short range-of-motion animation: a few frames that bend every major joint in turn. Scrub through it as you work. Riggers use the same kind of test to check a character before it goes to animation, so it is a habit worth building now.
Blender's Weight Paint mode has a handful of tools. You will use three of them for almost everything.
Draw is the main brush. Set the Weight value and the strength, then paint. The blend mode matters: Mix paints towards the weight you set, Add raises weights and Subtract lowers them. For blocking in, use full strength with a weight of 1 or 0. For refining, drop the strength a long way down and build up gradually.
Blur smooths the transition between weights, which is where most deformation problems live. A sharp jump from 1 to 0 across a single edge loop gives you a hard crease. Blurring spreads the change over several loops and gives you a softer bend.
Gradient lets you drag a straight or radial falloff across the mesh. It is the fastest way to get an even blend down a limb or across a twist zone, and much tidier than freehand brushing.
For exact values, turn on the vertex selection mask in Weight Paint mode so strokes only affect the vertices you select, or set a number directly in the sidebar (N) under Item, Vertex Weights. The Sample Weight tool picks up the weight under the cursor to reuse elsewhere.
Two settings in the tool options will save you hours.
Auto Normalize keeps the weights of all deform bones on each vertex adding up to 1. Without it, every stroke shifts the balance between bones in ways the heat map does not show: a vertex can read as fully red for the upper arm while the forearm still takes a large share of the movement. With it on, the weight you see is the influence you get. Turn it on for character work and leave it on.
Symmetry on X mirrors your strokes to the other side of the character, as long as the mesh is symmetrical and your bones follow Blender's naming convention (for example upper_arm.L and upper_arm.R). Name bones this way from the start.
Skin the body from the centre out. A good order is hips and spine, then legs, then arms and shoulders, then neck and head, and hands and fingers last. Lock each area once it works so you do not undo it by accident; the lock icon next to each vertex group in the Object Data properties does this.
For each joint, the same loop applies: pose it to the extreme, block in clear weights with Draw, soften the transition with Blur or Gradient, then scrub your range-of-motion animation and fix whatever breaks.
If the joint loses volume when it bends, the transition is usually too wide or centred in the wrong place. Keep the blend within two or three loops, centred on the joint, and make sure the back of the elbow or front of the knee holds its shape.
When a forearm or upper arm twists, a single bone pinches the mesh into a thin wrapper shape. Painting cannot solve this on its own. The fix is a twist bone (or two) along the limb, with weights blended gradually from the main bone to the twist bone. Rigify splits its arm and leg deform bones for the same reason, and most game skeletons include twist bones.
The shoulder is the hardest joint on any character. Paint it with the arm raised high and lowered, and check the chest and shoulder blade as well as the arm itself. Accept that some poses need correctives (extra helper bones or shape keys that fix a specific pose); weights alone will not handle every angle.
A single vertex on the foot that moves with the hand usually means a stray weight. Select the offending bone, look for unexpected colour in odd places, and subtract it. Then run Clean from the Weights menu to remove tiny weights you cannot see.
Game characters have rules that film characters do not, and weight painting is where many of them show up.
For the full rigging side, from building the armature to Rigify and export settings, read our guide to rigging in Blender for games.
Skinning is a core part of the rigger and technical artist roles in games, and studios look for it in portfolios. A reel that shows a character moving through extreme poses without breaking is far more convincing than a static turnaround. Show the weights, show the range-of-motion test and show the character in the engine.
The skill also transfers between software. Maya, which is widely used in game studios for rigging and animation, calls it painting skin weights, but the ideas are the same: normalised weights, smooth transitions, influence limits and testing in pose. Learn the principles properly in Blender and the switch is mostly a matter of new menus.
If you are new to 3D, start with the free Blender 3D Bootcamp. It is live online, the sessions are recorded, and a new cycle starts every three weeks, so you can build the modelling foundations that make rigging and weight painting click.
If you are ready to commit to games, the Certificate in 3D for Games is a 60-week online programme where you try 3D Art, Tech Art, Animation and Procedural before choosing your specialisation. The Tech Art specialisation covers rigging and skinning in Maya, plus Python, and every term ends in a team project: a walkable story environment, a playable level and a vertical slice. No 3D experience or portfolio is needed to apply.